Non-rigidly coupled, overlapping, non-feedback, optical systems for spatial filtering of fourier transform optical patterns and image shape content characterization

ABSTRACT

Non-rigidly coupled, overlapping, non-feedback optical systems for spatial filtering of Fourier transform optical patterns and image shape characterization comprises a first optical subsystem that includes a lens for focusing a polarized, coherent beam to a focal point, an image input device that spatially modulates phase positioned between the lens and the focal point, and a spatial filter at the Fourier transform pattern, and a second optical subsystem overlapping the first optical subsystem includes a projection lens and a detector. The second optical subsystem is optically coupled to the first optical subsystem.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to optical image processing.

2. State of the Prior Art

There are situations in which useful information can be derived fromspatially dispersed portions of light beams. In particular, when animage is being carried or propagated by a light beam, it may be usefulto gather and use or analyze information from a particular portion ofthe image, such as from a particular portion of a cross-section of abeam that is carrying an image. For example, in my U.S. Pat. Nos.6,678,411 and 7,103,223, which are incorporated herein by reference,narrow, radially oriented portions of a Fourier transform of an imageare captured and detected in the spatial domain and used to characterizeand encode images by shape for storage, searching, and retrieval. Asexplained therein, such radially oriented, angularly or rationallyspaced portions of light energy from a Fourier transform, i.e., Fouriertransform domain, of an image are captured sequentially in the spatialdomain, and such portions of the light energy detected in the spatialdomain are characteristic of the portions of the image content that aregenerally linearly aligned in the same angular orientation as the slitin the rotating mask when the light energy is detected. Those systemsperform the task of characterizing and encoding images by shape contentof the images quite well, but they still have several troublesomeshortcomings. For example, the optical systems are quite rigid withlittle flexibility or tolerance for imperfections in practical opticalcomponents or in selection and placement of such components in relationto each other, which results in inherent limitations that constrain theoutput to less than desirable quality and impose constraints on overallsize, optical layout, cost, and packaging.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and form a part ofthe specification, illustrate some, but not the only or exclusive,example embodiments and/or features of the present invention. It isintended that the examples and figures disclosed herein are to beconsidered as illustrative rather than limiting.

In the Drawings:

FIG. 1 is a schematic diagram of an optical image characterizer in whichan example non-rigidly coupled, non-feedback optical system according tothis invention is illustrated in an application for characterizing andencoding optical images by shape content to illustrate by example itsstructure and functional capabilities;

FIG. 2 is a schematic diagram of a simplified version of the exampleoptical system for explanation of its basic optical subsystems andcomponents;

FIG. 3 is a schematic diagram of an example implementation of theoptical system arranged to minimize or eliminate image blurring;

FIG. 4 is a perspective view of an example implementation of an opticalsystem according to the invention;

FIG. 5 is an isometric view of an example spatial light modulationdevice that can be used as a spatial filter component in this inventionillustrated with a beam of light focused on the light modulatingcomponents in the active optic area of the device;

FIG. 6 is a front elevation view of the light modulating components inthe active optic area of the spatial filtering spatial light modulatordevice in the shape of segmented modulator sectors that are oriented toextend radially at various angular orientations in relation to a centralaxis;

FIG. 7 is an enlarged, front elevation view of one sector of the active,light modulating components of the spatial light modulator device;

FIG. 8 is a cross-sectional view of a portion of an active optic sectorof a spatial light modulator for spatial filtering taken substantiallyalong section line 8-8 of FIG. 7;

FIGS. 9 a-c is an example spatial-domain image with large squares, whichis optically filtered in the Fourier transform domain to produce examplespatial domain images of low spatial frequency vertical and horizontalshape content;

FIGS. 10 a-c is an example spatial domain image with small squares,which is optically filtered in the Fourier transform domain to produceexample spatial domain images of high spatial frequency vertical andhorizontal shape content;

FIG. 11 illustrates a blank spatial domain image resulting fromactuation of a segment or sector in the Fourier transform plane that hasno incident light energy, thus no shape content;

FIG. 12 illustrates the active optic segmented sector of an examplesegmented radial spatial light modulator to facilitate explanation ofthe spatial optic filtering of the example images in FIGS. 9 a-c and 10a-c;

FIGS. 13 a-c include diagrammatic, elevation views of the active lightmodulating components of the example filtering spatial light modulatordevice to illustrate a use of an outer segment of a vertically orientedsector of the light modulation components along with diagrammatic viewsof an example image being characterized and a resulting detectable opticpattern that is characteristic of some of the vertically oriented shapecontent of the image;

FIGS. 14 a-c include diagrammatic, elevation views similar to FIGS. 13a-c, but illustrating a use of a near inner segment of the verticalsector;

FIGS. 15 a-c include diagrammatic, elevation views similar to FIGS. 13a-c, but illustrating a use of a near outer segment of an active opticsector that is oriented 45 degrees from vertical;

FIGS. 16 a-c include diagrammatic, elevation views similar to FIGS. 13a-c, but illustrating a use of the outer segment of the horizontaloriented active optic sector;

FIGS. 17 a-c include diagrammatic, elevation views similar to FIGS. 13a-c, but illustrating a use of the outer segment of the active opticsector that is oriented 191.25 degrees from vertical;

FIG. 18 is a diagrammatic elevation view similar to FIG. 13 a, butillustrating another example spatial light modulator device in which theactive optic segments are rectangular instead of wedge-shaped;

FIG. 19 is a diagrammatic elevation view of another example spatiallight modulator device in which groups of individually addressable lightsensors in a pixel array of sensors can be activated together inlocations that simulate sectors or segments of sectors to achieveangular and/or spatial analysis of a light beam for characterization ofan image by shape content for use as a spatial filter component in anoptical system according to this invention; and

FIG. 20 is a cross-section view similar to FIG. 8, but illustrating amodification in which a modulated light beam passes through, instead ofbeing reflected by, a segmented radial spatial light modulator inaccordance with this invention.

DETAILED DESCRIPTION OF EXAMPLE EMBODIMENTS

A system 10 for characterizing, encoding, and storing images by shapecontent of such images, as illustrated diagrammatically in FIG. 1 as anexample application and implementation of a non-rigidly coupled,overlapping, non-feedback optical system 800. In this example, imagecharacterizing, encoding, and storing system 10, any number n of images12, 14, . . . , n, can be characterized and encoded by the shape contentin such images, and such encoded shape information from each image canbe stored, for example, in database 102 for subsequent searching,retrieval, and comparison to shape content of other images that arecharacterized and encoded in the same manner. Some description of thisexample image characterizing, encoding, and storing system 10 is abeneficial aid to understanding the non-rigidly coupled, overlapping,non-feedback optical system 800.

The images 12, 14, . . . , n can be in virtually any form, for example,visual images on photographs, films, drawings, graphics, arbitrarypatterns, ordered patterns, or the like. They can also be stored and/orgenerated in or from digital formats or analog formats. Such images canhave content that is meaningful in some manner when viewed by humans, orthey can appear to be meaningless or not capable of being interpreted byhumans but characteristic of some other content, e.g., music, sounds,text, software, and the like. Essentially, any optic pattern of lightenergy intensities that can be manifested or displayed with discernableshape content can be characterized and encoded with this system 10.

A sample image 12, which can be obtained from any source (e.g.,Internet, electronic data base, web site, library, scanner, photograph,film strip, radar image, electronic still or moving video camera, andother sources) is entered into the optical image shape characterizer 10,as will be described in more detail below. Any number n of other sampleimages 14, . . . , n, are shown in FIG. 1 queued for entry in sequenceinto the optical image characterizer 10. Entry of any number n of suchsequential images 12, 14, . . . , n can be done manually or, preferably,in an automated manner, such as a mechanical slide handler, a computerimage generator, a film strip projector, an electronic still or videocamera, a hologram, or the like. The computer 20 in FIG. 1 is intendedto be symbolic of any apparatus or system that is capable of queuing andmoving images 12, 14, . . . , n into the image characterizer system 10.The example image 12 of an automobile displayed on the video monitor 22represents and is symbolic of any image that is placed in a process modefor characterizing and encoding its shape content in this system 10,although it should be understood that such display of the image beingprocessed is not an essential feature of this invention. The descriptionthat follows will, for the most part, refer only to the first image 12for convenience and simplicity, but with the understanding that it couldapply as well to any image 12, 14, . . . , n, etc.

In the example system 10 illustrated in FIG. 1, the image 12 is insertedinto the optical image characterizer system 10 in an image plane 19 thatis perpendicular to the plane of the view in FIG. 1. However, tofacilitate explanation, illustration, and understanding of theinvention, the images 12, 14, . . . , n are also shown in phantom linesin the plane of the view in FIG. 1, i.e., in the plane of the paper.This same convention is also used to project image 12′ produced by theE-SLM 26, the Fourier transform optic pattern 32, the active optic area54 of the filtering spatial light modulator (SLM₂) 50, isolated andfiltered optic pattern 60, and the detector grid 82 from theirrespective planes perpendicular to the plane of the paper for purposesof explanation, illustration, and understanding. These components andtheir functions in the image characterizer system 10 will be explainedin more detail below.

As mentioned above, the image 12 can be entered into the optical imagecharacterizer system 10 by the computer 20 and electronicallyaddressable spatial light modulator (E-SLM) 26, which produces amonochromatic version 12′ of the image 12, as will be described in moredetail below. The light beam 25 that is incident on the SLM₁ 26 is alsodiffracted on a pixel-by-pixel basis. The liquid crystal material in theimage-producing SLM₁ 26 forms a Fourier transform (FT) optic pattern 32,which is unique to the image 12′, at the Fourier transform (FT) plane 33where the beam 25, 27 is focused to a point 31 by the lenses 30 a and 30b. Even though it is not recognizable as the image 12′ to the human eyeand brain, the complex amplitude distribution of light energy 34 in theoptic pattern 32 is the Fourier transform of the complex lightdistribution in the image 12′, which can be characterized byintensities, i.e., amplitudes, of light energy distributed spatiallyacross the optic pattern 32. Of course, persons skilled in the art willalso recognize that an E-SLM is only one of a number of well-knowndevices, including, but not limited to, optically addressable spatiallight modulators, that can create the image 12′ in monochromatic,diffracted light, and this invention is not limited to this particularexample.

Concentrations of intense light energy in the Fourier transform (FT)optic pattern 32 at the Fourier transform plane 33 generally correspondto spatial frequencies of the image 12′, i.e., how closely together orfar apart features in the image 12′ change or remain the same. In otherwords, spatial frequencies are also manifested by how closely togetheror far apart light energy intensities across the light beam 27 change orremain the same. For example, a shirt with a plaid fabric in an image(not shown), i.e., having many small squares, would have a higherspatial frequency, i.e., changes per unit of distance, than a plain,single-color shirt (not shown) in the image. Likewise, portions of animage, such as the bumper and grill parts 35 of the example automobilein image 12′, would have a higher spatial frequency than the side panel36 portion of the automobile image 12′, because the bumper and grillparts 35 comprise many small pieces with various edges, curves, andother intricate changes within a small spatial distance, whereas theside panel 36 is fairly smooth and uniform over a large spatialdistance. Light energy from the finer and sharper details of an image(more spatial frequency), such as the more intricate bumper and grillparts 35 of the image 12′, tend to be dispersed farther radially outwardfrom the optical center or axis 40 in the Fourier transformed image 32than light energy from more course or plain details of an image (lessspatial frequency), such as the side panel 36 of the image 12′. Theamplitude of light energy 34 dispersed radially outward in the Fouriertransform optic pattern 32 is related to the light energy of thecorresponding portions of the optic pattern of image 12′ from which suchlight energy emanates, except that such light energy is concentratedinto areas or bands 34 at the plane 33 of the Fourier transform (FT)optic pattern 32, i.e., into bands of intense light energy separated bybands of little or no light energy, which result from constructive anddestructive interference of the diffracted light energy. If the highspatial frequency portions of the image 12′, such as the bumper andgrill portion 35, are bright, then the intensity or amplitude of lightenergy from those high spatial frequency portions of the image 12′,which are dispersed to the more radially outward bands of light energy34 in the Fourier transform optic pattern 32, will be higher, i.e.,brighter. On the other hand, if the high spatial frequency portions ofthe optic pattern of image 12′ are dim, then the intensity or amplitudeof light energy from those high spatial frequency portions of the opticpattern of image 12′, which are dispersed to the more radially outwardbands of light energy 34 in the Fourier transform optic pattern 32, willbe lower, i.e., not so bright. Likewise, if the low spatial frequencyportions of the optic pattern of image 12′, such as the side panelportion 36, are bright, then the intensity or amplitude of light energyfrom those low spatial frequency portions of the optic pattern of image12′ which are dispersed by the FT lens to the less radially outwardbands of light energy 34 in the Fourier transform optic pattern 32(i.e., closer to the optical axis 40), will be higher, i.e., brighter.However, if the low spatial frequency portions of the optic pattern ofimage 12′ are dim, then the intensity or amplitude of light energy fromthose low spatial frequency portions of the optic pattern of image 12′,which are dispersed by the FT lens 30 to the less radially outward bandsof light energy 34 in the Fourier transform optic pattern 32, will belower, i.e., not so bright.

In summary, the Fourier transform optic pattern 32 of the lightemanating from the image 12′: (i) is unique to the image 12′; (ii)comprises areas or bands of light energy 34 concentration, which aredispersed radially from the center or optical axis 40, that representspatial frequencies, i.e., fineness of details, in the image 12′; (iii)the intensity or amplitudes of light energy 34 at each spatial frequencyarea or band in the Fourier transform optic pattern 32 corresponds tobrightness or intensity of light energy emanating from the respectivefine or course features of the image 12′; and (iv) such light energy 34in the areas or bands of the Fourier transform optic pattern 32 aredetectable in intensity and in spatial location by this optical imagecharacterizer system 10.

Since this optical image characterizer system 10 of this invention isdesigned to characterize an image 12 by shapes that comprise the image12, additional sectorized spatial filtering of the Fourier transformlight energy pattern 32 is used to detect and capture light energyemanating from the finer or sharper details or parts of such finer orsharper details in the image 12′, which are aligned linearly in variousspecific angular orientations. Such sectorized spatial filtering can beaccomplished in any of a number of different ways, as will be explainedin more detail below, but an example sectorized spatial filterarrangement for this function is included in a combination of thesegmented radial spatial light modulator device (SLM₁) 50, which isdescribed in U.S. Pat. No. 7,103,223, together with the polarizer orpolarization analyzer 70. Essentially, the segmented radial SLM₁ device50 rotates the plane of polarization of selected sector portions of theFourier transform optic pattern 32 from p-plane polarization to s-planepolarization, or vice versa, and the polarizer/analyzer 70 separateslight energy of those portions of the beam 27 that are isolated andpolarized in one plane from the light energy of the rest of the Fouriertransform optic pattern 32 that remains polarized in the other plane sothat such light energy of the selected and isolated portions can bedetected separately at the detector 80, as will be described in moredetail below. A rotating mask with a radial slot (not shown), such asthat described in U.S. Pat. No. 6,678,411, could also be used for thesectorized spatial filter 50 in the example optical system 800.

In the optical image characterizer 10 illustrated in FIG. 1, the image12 has to be recreated with monochromatic, coherent light energy, e.g.,at image 12′. For example, a monochromatic image 12′ can be recreatedwith a spatial light modulator (SLM₁) 26 illuminated with a beam ofmonochromatic light 24 from a light source 23, such as a laser diode orgas diode. The spatial light modulator (SLM₁) 26 can be opticallyaddressable (O-SLM), such as the one illustrated in U.S. Pat. No.6,678,411, or it can be electrically addressable (E-SLM) and driven, forexample, by a computer 20 in FIG. 1 or by a video camera (not shown). Asis known by persons skilled in the art, a spatial light modulator (SLM)can “write” an image into a polarized beam of light 25 by rotating orpartially rotating the polarization plane of the light on a spatialbasis across the beam 25 so that, upon reflection as beam 27, it iseither transmitted through, or blocked by, the polarizer 116, dependingon what is needed to create the image 12′ in monochromatic light. In anoptically addressed SLM (not shown), the image plane is addressed on aspatial basis by incident light energy on a semiconductor materialadjacent the polarization rotating material (usually a liquid crystalmaterial), whereas, in an electrically addressable SLM 26, the liquidcrystal, polarization rotating material is addressed electrically on apixel-by-pixel basis. The pixel portions of the polarized light thathave the plane of polarization rotated 45 degrees as they pass oncethrough the liquid crystal material, whereupon such light is reflectedand passed back through the liquid crystal again, where it is rotatedanother 45 degrees. Thus, the pixels of light in polarized beam 25 thathave their plane of polarization rotated in the SLM₁ 26 are reflectedand emerge from the SLM₁ 26 along the optical path 27, which has anoptical axis 40, in a pattern imposed by the SLM₁ 26 that forms an image12′ and with its plane of polarization rotated 90 degrees from the planeof polarization of the incident beam 25. The remaining pixels of lightin the emerging beam 27, which do not undergo rotation of the plane ofpolarization, are also reflected, but they can be separated or strippedfrom those that have undergone rotation of plane of polarization, aswill be explained below. Various light intensities or brightnesses ofthe image 12 can be recreated in gray scales in the monochromatic image12′ by partial rotations of plane of polarization on a pixel-by-pixelbasis.

In the FIG. 1 example embodiment, the monochromatic, coherent light beam24 from laser source 23 provides the light energy that is utilized tocarry the shape content of the image 12′ for further analysis,characterization, and encoding. It may already be polarized by thebuilt-in optics of the laser source 23. If desired or necessary, thepolarization of the initial beam portion 24 can be purified orconditioned by passing it through an optional polarizer 28 to providethe polarized beam of coherent light 25 with all the light polarized inone plane, such as, for example, but not for limitation, in the s-plane,as indicated by 25(s). Of course, the initial beam portion 25 could bep-polarized, instead of s-polarized to implement this invention withinverses of the example planes of polarization illustrated in FIG. 1 anddescribed herein, which would work just as well. Therefore, while theexample optical system 800 is described for convenience with aparticular sequence of s and p polarizations, opposite or inversepolarizations are considered to be equivalents. Optional spectralmirrors 802 and 804 can be provided to fold the beam 24 from the lasersource 23 into a convenient optical path.

The focusing lenses 30 a and 30 b, optional polarizer 28,image-producing SLM₁ 26, polarizer/analyzer 116, optional polarizationrotator 118, and sectorized spatial filter 50 comprise a firstoverlapping optical subsystem 810 that produces the Fourier transformpattern 32 of the monochromatic image 12′, as will be explained in moredetail below. The projecting lenses 78 a and 78 b, polarizer/analyzer70, and detector 80 comprise a second overlapping optical subsystem 820that projects the sectorized, spatially filtered, image 60 fordetection, as will be described in more detail below. The optionalspectral mirror 806 can also be provided to fold the second overlappingoptical subsystem 820 into a compact form.

As mentioned above, the focusing lenses 30 a and 30 b are provided tofocus the polarized, monochromatic, coherent beam portions 25, 27 to aspot, i.e., focal point 31, on the sectorized spatial filter 50, so thatthe Fourier transform pattern 32 forms on a Fourier transform plane thatcontains the focal point 31, but which in one example embodiment is atan angle to the focal plane 33 to prevent feedback that would blur ordegrade the Fourier transform pattern and filtered spatial image at thedetector 80, as will be explained in more detail below. As alsomentioned above, this description will proceed for convenience with thebeam portion 25 that is incident on the image-producing SLM₁ 26designated as polarized in the s plane, i.e., s-polarized, although itcould just as well be p-polarized. The focusing function of lenses 30 aand 30 b could also be accomplished with a single lens or anycombination of lenses, as would be apparent to persons skilled in theart, and any such other focusing system that focuses beam portions 25,27 to a point on the spatial filtering SLM₂ is considered to beequivalent. If the optional polarizer 28 is used and positioned betweenthe two focusing lenses 30 a and 30 b, as shown in FIG. 1, the firstlens 30 a can be shaped and positioned to collimate the beam portion 24between the two lenses 30 a and 30 b to minimize or prevent uneven pathlengths and other deleterious effects in the polarizer 28, especially ifthe beam portion 24 is flared, as will be discussed below.

As mentioned above, there are many ways of “writing” images 12, 14, . .. , n into a light beam, one of which is with an electronicallyaddressable SLM. In this example, computer 20 has the content of image12 digitized, so the computer 20 can transmit digital signals via link21 to the electronically addressable SLM₁ 26 in a manner that addressesand activates certain pixels in the electronically addressable SLM 26 ₁to “write” the image 12′ into reflected light beam 27(p), as isunderstood by persons skilled in the art. Essentially, the addressedpixels rotate the plane of polarization by 90 degrees from the s-planeof incident beam 25(s) to the p-plane of reflected beam 27(p), or bysome lesser amount for gray-scales, in a manner such that the reflectedlight energy with partially or fully 90-degree polarization planerotation is in a monochromatic optical pattern of the image 12′. Ofcourse, persons skilled in the art will also understand that the image12′ could also be created with an electronically addressable SLM thatoperates in an opposite manner, i.e., the plane of polarization isrotated in reflected light, except where pixels are activated, in whichcase the computer 20 would be programmed to activate pixels according toa negative of the image 12 in order to write the image 12′ intoreflected beam portion 27. Either way, the emerging beam portion 27 ofcoherent light, carrying image 12′, is p-polarized instead ofs-polarized or vice versa. Consequently, in this example, themonochromatic light beam portion 27(p), with its light energydistributed in an optic pattern that forms the monochromatic image 12′,is transmitted by the polarizer/analyzer 116 to the sectorized spatialfilter 50 and beyond, instead of being absorbed or reflected by it.

As persons skilled in the art understand, the orientation of the lightpolarization has to match the imaging SLM₁ 26 polarization in order forthe imaging SLM₁ 26 to operate effectively. If the optics in the lasersource 23 do not provide for adjusting polarization plane adjustment,such matching can be accomplished by rotating the entire laser source 23about its longitudinal axis, or an optional polarization rotatorcomponent, such as a half-wave retarder (not shown) can be positioned inthe beam portion 24 or 25 in front of the imaging SLM₁ 26 and rotated anappropriate amount to achieve the desired polarization planeorientation.

The polarizer/analyzer 116 can be any device that separates p-polarizedlight from s-polarized light or vice versa. Such devices are well-knownand could be, for example, an absorbing polarizer 116, as shown in FIG.1, which transmits the p-polarized light and absorbs, thus blocks, thes-polarized light. Another suitable example polarizer/analyzer could bea polarizing beam splitter, which may transmit p-polarized light in onedirection and reflect s-polarized light in another direction, or viceversa. The result, as shown in FIG. 1, is that the beam portion 27 afterthe polarizer/analyzer 116 comprises only p-polarized light, which isdesignated as 27(p).

As shown in FIG. 1, the incoming beam portion 25(s) is shown with anangle of incidence a to the normal optic axis 808 of the SLM₁ 26, so thereflected beam 27 also has an angle α to the normal optic axis 808. Thisfeature is not essential, but it beneficially prevents undesirablepseudo-p feedback formed from unintended reflection of s-polarized lightby the polarizer/analyzer 116, which would otherwise blur or otherwisedegrade the Fourier transform pattern 32 and resulting filtered spatialimage 60 at the detector 80, as will be explained in more detail below.

As mentioned above, the sectorized spatial filter 50 can be a spatiallight modulator (SLM₂) with pixel groups or other active opticalelements that rotate polarization of light in radially extending sectorsand/or segments of sectors at selected angular orientations to filterlight energy in the Fourier transform pattern 32, as will be describedin more detail below. For example, the sectorized spatial filter SLM₂ 50depicted in FIG. 1 can rotate the incident p-polarized light from beamportion 27(p) in a sector 500 to s-polarized light in the beam portion61 reflected from the SLM₂ spatial filter 50, while the rest of thereflected light in beam portion 61 remains p-polarized light.Consequently, since the sector 500 is positioned in the plane of theFourier transform image pattern 32, the portion of the light 34 in theFourier transform pattern 32 in the sector 500 is rotated to s-polarizedlight while the rest of the light 34 in the Fourier transform pattern 32remains p-polarized, and both that s-polarized and p-polarized light arepropagated in beam portion 61 into the second overlapping opticalsubsystem 820. The optional polarization rotator 118, for example, ahalf-wave retarder, positioned in the beam portion 27(p) can be used toadjust the polarization of beam portion 27(p) to match the polarizationof the liquid crystal material in the spatial filtering SLM₂ 50.

The second overlapping optical subsystem 820 projects the light energyof the filtered, monochromatic, spatial image 12′ to the detector 80. Todo so, the projection lenses 78 a and 78 b are shaped and positioned toproject the spatial image 12′ at the SLM₁ 26 as the object onto thedetector 80 as the real image, which requires only that the distancefrom the object, i.e., image 12′ at SLM₁ 26, to the detector 80 has tobe greater than the focal length of the combination of lenses 78 a and78 b. Consequently, there is great flexibility in lens parameters, suchas size and focal length, and in placement of the projection lenses 78 aand 78 b and detector 80 in relation to each other and in relation tothe imaging SLM₁ 26, spatial filtering SLM₂ 50, and other components ofthe first overlapping optical subsystem 810. Such flexibility is usefulin many ways. One example is the ability to scale the projected,filtered image to the size of the detector, including, for example, tomatch pixels or groups of pixels of the image 12′ from the imaging SLM₁26 and/or the filtering SLM₂ 50 to different sized sensors or groups ofsensors in the detector 80.

The polarizer/analyzer 70 separates the p-polarized light in beamportion 61 from the s-polarized light so that only the desired portionof the spatially filtered light from the Fourier transform pattern 32reaches the detector 80. For example, if the polarizer/analyzer 70 is anabsorbing polarizer, as shown in FIG. 1, it can transmit either thes-polarized light or the p-polarized light, as desired, and absorb, thusblock the opposite polarization. A polarizing beam splitter couldprovide a similar result by transmitting one polarization orientationand reflecting the other out of the system. In the FIG. 1 example, thepolarizer/analyzer 70 transmits the s-polarized light and blocks thep-polarized light so that the beam portion 61(s) after thepolarizer/analyzer 70 has only the s-polarized light that is selected byspatially filtering the Fourier transform pattern 32 with the SLM₂ 50,so that only that s-polarized light from the sector 500 reaches thedetector 80. If, on the other hand, only the p-polarized light in beamportion 61 was allowed to pass to the detector 80, then the detectorwould detect all of the light from the Fourier transform pattern 32except the light from the sector 500. Either of these methods can beused. Also, while the spatial filter 50 is described for the exampleshape characterizing application as being sectorized, e.g., with sector500 and similar sectors and segments of sectors, it can have any otherspatial filter configuration as may be desired for other Fouriertransform pattern filtering applications in which this non-rigidlycoupled, overlapping non-feedback optical system 800 may be used.

The concept, structure, and function of the non-rigidly coupled,overlapping optical systems 810, 820 can be illustrated, for example, byFIG. 2, recognizing that it is simplified and not exactly the samestructure as the system 800 shown in FIG. 1. For example, theimage-producing SLM₁ 26′ in FIG. 2 is illustrated as a transmitting,rather than a reflecting, SLM, and all of the components are rangedalong a straight line beam axis 40, rather than folded, in order toillustrate more graphically the non-rigidly coupled, overlapping natureof the two optical systems 810, 820. Also, for simplicity, the twofocusing lenses 30 a and 30 b in FIG. 1 are depicted as one focus lens30 in FIG. 2, and the two projection lenses 78 a and 78 b in FIG. 1 aredepicted as one projection lens 78 in FIG. 2.

As shown in FIG. 2, the incoming beam 24 from a laser source (not shown)passes through the polarizer 28 for conditioning or purifying thes-polarization and then through the focusing lens 30, which focuses thebeam portions 25(s) and 27(p) to a focal point 31, which defines thefocal plane 33 at a focal distance F, from the lens 30. Theimage-producing SLM₁ 26 is positioned in the beam portion 25(s), whichilluminates the SLM₁ 26 with the s-polarized light. The image 12′ is“written” in the beam portion 27 by the image-producing SLM₁ 26, asexplained above, and the image-producing SLM₁ 26 is flat so that itimposes phase modulations and diffracts the beam portion 27 so that thediffracted light rays form a Fourier transform pattern 32 of the image12′ at the focal plane 33.

The flat SLM₁ 26 will impose phase changes regardless of the directionof the incident light rays, so the incoming beam 24 does not have to becollimated to form a Fourier transform pattern of the image 12′ at thefocal point 31 of the lens 30, as it would have to be if refraction bythe lens 30 was being used to form the Fourier transform pattern 32.Therefore, the incoming beam 24 can be diverging from the optical axis40, as shown in FIG. 2, which can be beneficial for sizing the beamportion 25(s) to illuminate enough of the image-producing area of theSLM₁ 26 to include the entire pixel image 12, which is necessary toavoid losing shape content or features from the original image 12 in theSLM-formed, monochromatic image 12′.

The SLM₁ 26 forms the monochromatic image 12′ in the light beam portion27 by rotating plane of polarization on a pixel-by-pixel basis, so that,for example, the rotated, p-polarized light in beam portion 27 comprisesthe monochromatic image 12′, and the unrotated, s-polarized light isblocked by the polarizer/analyzer 116. The p-polarized, diffracted lightof the image 12′ is transmitted by the polarizer/analyzer 116 so that itinterferes and forms the Fourier transform 32 of the image 12′ at thefocal plane 33 of the focusing lens 30.

Consequently, the only rigid optical and spatial constraints in thefirst overlapping subsystem 810 are that the incoming beam 24 has to bemonochromatic and coherent light, the lens 30 has to have a focal point31, the image-producing SLM₁ 26 has to be positioned somewhere betweenthe focusing lens 30 and the focal point 31 where whatever image 12 itpresents is fully illuminated, and the spatial filter 50 has to bepositioned where the Fourier transform pattern 32 of the monochromaticimage 12′ is presented, i.e., at the focal point 31, or, optionally, atsome other projection of the Fourier transform pattern which could bedone with another lens (not shown), if desired. In the FIG. 2 example,the spatial filtering SLM₂ 50 is in the focal plane 33, which can alsobe called the Fourier transform plane in this example linear beam axisconfiguration. Also, in the FIG. 2 example, the spatial filtering SLM₂50 is shown as a transmitting SLM instead of a reflecting SLM, whichperforms the same spatial filtering function, but the s-polarized andp-polarized pixels of light are transmitted through the SLM₂ 50 insteadof reflected as in the FIG. 1 example described above.

Referring again primarily to FIG. 2, the spatial image projectionsubsystem 820 is positioned to optically overlap the imaging andfiltering subsystem 810 in a non-rigid manner, i.e., with distancerelationships between components that have some flexibility or leewaywithin certain parameters. In this arrangement, the projection lens 78is positioned to project the spatial domain image 12′ from the spatialimage producing SLM₁ 26 onto the detector 80, the only distanceparameters coupling the first subsystem 810 to the second subsystem 820being that the spatial filtering SLM₂ 50 is positioned someplace betweenthe image-producing SLM₁ 26 and the projection lens 78 and that theimage 12′ is outside the focal distance F₂ of the projection lens 78.Also, the polarizer/analyzer 70 has to be positioned somewhere betweenthe spatial filtering SLM₂ 50 and the detector 80, and it can be oneither side of the projection lens 78. Therefore, while the projectionlens 78 effectively reaches through the spatial filtering SLM₂ 50 toproject the spatial domain image 12′ onto the detector 80, the onlylight rays from the spatial domain image 12′ that get projected by theprojection lens 78 onto the detector 80 are those that have beenspatially filtered in the Fourier transform domain by the spatialfiltering SLM₂ 50 and that pass through the polarizer/analyzer 70.

Consequently, only the desired portion of the spatial domain image 12′,as selected by the Fourier domain filtering of SLM₂ 50, gets projectedby the projection lens 78 to form the filtered spatial domain image 60at the detector 80. In other words, the spatial domain image 60 iscomprised of only the parts of the spatial domain image 12′ that areselected in the Fourier transform domain. In the example image shapecharacterizing and encoding application described herein, those partsare the portions of the light rays from the image 12′ that pass throughradially extending sectors or segments of sectors in the Fouriertransform domain, but they could be any other selected parts filtered inany other way in the Fourier transform domain.

As mentioned above, there is considerable flexibility in componentplacement. The projection lens 78 has to be between the image producingSLM, 26 and the detector 80 and must have both of its focal points 822,824 between the image producing SLM₁ 26 and the detector 80, and thespatial filtering SLM₂ 50 has to be optically between the imageproducing SLM₁ 26 and the projection lens 78. However, those componentscan be moved or positioned just about anywhere desired within thoseconstraints, depending on practical size and capabilities of thecomponents.

The non-feedback arrangement of the system 800 is shown in more detailin FIG. 3. As described above, the beam 24 is shown in FIG. 3 projectedfrom the laser source 23 in a slightly flared state, i.e., with a flareangle β from parallel to the beam axis, for example, five degrees (5°),to facilitate illumination of the entire image 12 as it is presented onthe imaging SLM₁ 26. The focusing lenses 30 a and 30 b focus the beamportion 25(s), illustrated in FIG. 3 as s-polarized for example only, toa focal point 31 on the spatial filtering SLM₂ 50, while the imagingSLM₁ 26 is positioned in the s-polarized beam 25(s) anywhere between thefocusing lenses 30 a, 30 b and the spatial filtering SLM₂ 50, where itspixels of the input image 12 are fully illuminated. The imaging SLM₁ 26produces the monochromatic image 12′ in beam portion 27, e.g., byreorienting pixel portions of a liquid crystal molecules to rotate thepolarization of light for the image 12′ to p-polarization, which alsoinduces phase changes in the light on a pixel-by-pixel basis. Suchpixilated phase changes in the flat image-producing plane of the SLM₁ 26result in diffraction of the p-polarized pixels of light of themonochromatic image 12′ produced by the SLM₁, the extent of suchdiffraction for each pixel of light depending on the extent of phasechange induced by the liquid crystal material as it rotates or partiallyrotates polarization plane in such crystals. The remaining s-polarizedlight is blocked by the absorbing polarizer/analyzer 116 from reachingthe spatial filtering SLM₂ 50 and detector 80. The diffracted rays oflight that comprise the monochromatic image 12′ from the imaging SLM₁propagate toward the spatial filtering SLM₂ 50 to form the Fouriertransform pattern 32 of the light at the SLM₂ 50. Whilepolarizer/analyzers are quite good at separating p-polarization froms-polarization and vice versa, in reality there is some reflection oflight back toward the imaging SLM₁ 26, regardless of whether thepolarizer/analyzer 116 is an absorbing polarizer/analyzer, such as thatillustrated in FIG. 3, or a polarizing beam splitter, such as thepolarizing beam splitters shown in U.S. Pat. Nos. 6,678,441 and7,103,223. The inevitable reflection of a small amount of p-polarizedlight by the polarizer/analyzer 116 just means a slight diminution ofthe intensity of the p-polarized, diffracted light from image 12′ thatis incident on the spatial filtering SLM₂ 50, thus also a slightdiminution of the intensity of the image portion 60 at the detector 80,which is usually not a problem. However, the inevitable concurrentreflection of a small amount of the s-polarized light by thepolarizer/analyzer 116, as illustrated diagrammatically by theretro-arrows 812 in FIG. 3, would be a problem if the imaging SLM₁ 26was perpendicular to the axis 40′ of the beam portion 27, as it is, forexample, in U.S. Pat. No. 6,678,411 and in U.S. Pat. No. 7,103,223. Theproblem would occur because the s-polarized light is not part of thep-polarized image 12′ and should never reach either the spatialfiltering SLM₂ 50 or the detector 80. Yet, the reflected portion 812 ofthe s-polarized light at the polarizer/analyzer 116 propagates back tothe imaging SLM₁ 26, where it can be rotated to p-polarization, justlike the incident beam 25(s). If the axis 40′ of the beam portion 27 wasperpendicular to the reflection plane 19 of the imaging SLM₁ 26, suchrotation of the unwanted, s-polarized reflection 812 by the imaging SLM₁26 to p-polarized light would be propagated back again to thepolarizer/analyzer 116, and because it is now p-polarized, would then betransmitted by the polarizer/analyzer 116 along with the desiredp-polarized light of the image 12′ to the spatial filtering SLM₂ 50.Thus, such reflected s-polarized light would feed back to thepolarizer/analyzer 116 as “pseudo p-polarized” light and, if notfiltered out by the spatial filtering SLM₂ 50, would continuepropagating all the way to the detector 80. Since such unwanted“pseudo-p polarized” light feedback would have effectively traveledfarther than the main beam, it would superimpose multiple, differentversions of the image 12′ in different scales onto the main image 12′and distort and/or generally degrade the quality of the resultingfiltered image 60 at the detector 80. To avoid this problem of suchreflected, s-polarized light fraction 812 from returning as unwanted“pseudo-p polarized” light feedback to degrade the image 60 at thedetector 80, the imaging SLM₁ 26 is oriented in FIG. 3 with itsimage-producing and reflection plane 19 at an angle θ of less than 90°to the axis 40 of the incident beam portion 25(s), so the angle ofincidence α of the incident beam 25(s) at the imaging SLM₁ 26 is greaterthan 0°. Therefore, the axis 40′ of reflected beam portion 27 from theSLM₁ 26 is also at the angle α from the normal 39 of the reflectionplane 19 of the SLM₁ 26. Consequently, any unwanted s-polarized light812 reflected by the polarizer/analyzer 116 will not be reflected by theimaging SLM₁ 26 back to the polarizer/analyzer 116, spatial filteringSLM₂ 50, and detector 80, even if it is rotated by the imaging SLM₁ 26to p-polarized light, but will instead be reflected back in thedirection of incoming beam 25(s), as indicated by arrows 814, to thepolarizer 28, where it will be absorbed or blocked. If the polarizer 28is not used, such unwanted, reflected light 814 could return to thelaser source 23, where it could be blocked by optical components usuallybuilt into such laser sources, or slight deviations or imperfections incomponent alignments could cause it to just be reflected out of thesystem.

Because the monochromatic image 12′ is formed by the imaging SLM₁ 26 ina imaging plane 19 at the angle θ to the axis 40 of the incoming beamportion 25(s), it is also at the same angle θ to the axis 40′ of thereflected beam portion 27, which comprises the image 12′, and the image12′ is also at the angle α to a plane 816 that is perpendicular to theaxis 40′ of beam portion 27. Consequently, the Fourier transform pattern32 of the image 12′ will form in a plane 818, which includes the focalpoint 31 on the axis 40′ of the beam portion 27, but which is opticallyparallel to the imaging plane 19 and at the angle θ to the axis 40′,instead of in the focal plane 33. In other words, the Fourier transformpattern 32 forms in a Fourier transform plane 818, which is at the angleα to the focal plane 33. Therefore, to prevent distortion and to getprecise spatial filtering in the plane 818 of the Fourier transformpattern 32, the spatial imaging SLM₂ 50 is positioned so that itsfiltering plane is at the focal point 31, but in the plane 818 of theFourier transform pattern 32, not in the focal plane 33. In other words,the filtering plane of the spatial filtering SLM₂ 50 is positioned onthe focal point 31, but oriented optically parallel to the imaging plane19 of the imaging SLM₁ 26, which can be accomplished by positioning thefiltering plane physically parallel to the imaging plane 19. If aspectral mirror (not shown) was placed in the beam portion 27, the beamportion 27 could be folded to put the filtering plane 818 of the spatialfiltering SLM₂ 50 so that it is positioned on the focal point 31, butoriented perpendicular to the imaging plane 19 of the imaging SLM₁ 26,if desired for packaging or other purposes, which would still beeffectively optically parallel to the imaging plane 19.

As explained above, the spatial filtering SLM₂ 50 spatially filters theFourier transform pattern 32 of the image 12′, and the projection lenses78 a and 78 b reach back through the spatial filtering SLM₂ 50 toproject the spatial domain image 12′, as filtered by the SLM₂ 50, ontothe detector 80 as the filtered, spatial domain image 60. Therefore, toprevent distortion of the filtered, spatial domain image 60 at thedetector 80, the detection plane 826 of the detector 80 also has to beoptically parallel to the imaging plane 19 of the imaging SLM₁ 26. Inthe FIG. 3 example, the spectral mirror 806 is provided to fold the beamportion 61(s) in order to orient the detection plane 826 perpendicularto the imaging plane 19 for compact packaging purposes, which iseffectively optically parallel. Of course, the detection plane 826 canbe positioned physically parallel to the imaging plane 19 to beoptically parallel.

To avoid the “pseudo-p polarization” feedback problem described above,the incident angle α can be any angle that causes the unwanted light tomiss the detector. In one example implementation, the incident angle αis chosen to be 13.5° because it provides for a compact system layoutwith sufficient room for the necessary components and is great enough to“skew” the unwanted reflection far enough to miss the detector 80, asexplained above. Such an example layout of the optical image spatialfiltering system 800 described above is illustrated in FIG. 4, where thecomponents are designated by the same numbers as those used in the FIG.3 schematic diagram.

An example segmented radial spatial light modulator (SLM) device 50 isillustrated diagrammatically in FIG. 5 with a beam of light 27(p)focused on the active optic area 54 in the center portion of thesegmented radial SLM device 50. As illustrated diagrammatically in FIG.5, the segmented radial SLM device 50 is preferably, but notnecessarily, constructed as an integrated circuit 52 mounted on a chip56 equipped with a plurality of electrical pins 58 configured to beplugged into a correspondingly configured receptacle (not shown) on aprinted circuit board (not shown). In such an embodiment, the pins 58are connected electrically by a plurality of wires 59 soldered tocontact pads 55 of the integrated circuit 52 to enable addressing andoperating optic components in the active optic area 54, as will bediscussed in more detail below.

An enlarged elevation view of the active optic area 54 of the integratedcircuit 52 is illustrated in FIG. 6, and an even more enlarged view ofthe active optic segments 502, 504, 506, 508 of one modulator sector 500(sometimes hereinafter “sector” for convenience) of the active opticarea 54 is illustrated in FIG. 7. Essentially, the segmented radial SLMdevice 50 is capable of selectively isolating radially disposed portionsof the incident light energy at various angular orientations in relationto a central axis 40′ for detection, as will be explained in more detailbelow. One way of accomplishing such isolation is by reflecting, as wellas rotating plane of polarization of, the selected radially disposedportions of the light beam 27(p) that is incident on the active opticarea 54, while other portions of the light beam 27(p) are reflected, butwithout rotation of the plane of polarization, or vice versa. In thepreferred embodiment, each of the active optic segments, such assegments 502, 504, 506, 508 of sector 500 in FIG. 7, are addressableindividually through electrically conductive traces 503, 505, 507, 509,respectively, although the invention also can be implemented, albeitwith less spatial frequency or scale resolution, by a sector 500comprising only one active optic modulator or by activating one or moreof the individual segments simultaneously.

The selection and isolation of a portion of the incident light beam27(p) is illustrated in FIG. 8, which is a partial cross-section ofactive optic segments 506, 508. An incident light beam 27(p), which isdesignated, for example as being p-polarized, i.e., polarized in thep-plane, will be reflected by, and will emerge from, segment 508 ass-polarized light 27(s), i.e., light polarized in the s-plane, or viceversa, when the segment 508 is activated by a voltage V on trace 509,while the unactivated segment 506 reflects, but does not rotate plane ofpolarization of, the incident light 27(p). In FIG. 8, the lightreflected by the activated segment 508 is designated as 61(s) toindicate its s-plane polarization, while light reflected by thenon-activated segment 506 is designated as 61(p) to indicate its p-planepolarization. The structure and function of the segments 506, 508, whichare typical of all the segments of all the sectors 500, 510, 520, 530,540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 of the activeoptic area 54, will be explained in more detail below. Suffice it to sayat this point that a s-polarization plane is orthogonal to, i.e.,rotated 90° in relation to, a p-polarization plane and that suchrotation of plane of polarization of a portion of an incident light beam27 or vice versa, (p) (see FIGS. 5 and 8 and 4) to s-polarization 61 (s)(see FIG. 8), while simultaneously leaving other portions of theincident beam 27(p) unrotated in the reflection 61(p), enablesfiltration or separation of that portion 61(s) from the remainder of thelight beam 61(p), or vice versa, as will be explained in more detailbelow. Of course, as mentioned above, incident beam 27 could bes-polarized, and the device 52 could rotate a portion of such anincident beam to p-polarization to enable filtration or separation. Suchalternatives are all readily understood by persons skilled in the art aseffective equivalents, and this invention does not require or prefer oneof such alternatives over others. Therefore, for simplicity, one orseveral of such alternatives will be explained, but with theunderstanding that such inverses or alternatives are implicit, thuscovered by such explanation and claims.

In the example segmented, radial SLM 50 shown in FIGS. 5-8 only theportions of the light energy 34 in the Fourier transform pattern 32 thatalign linearly with selected active optic segments, for example, segment502, 504, 506, and/or 508 (FIG. 7), have the plane of polarizationrotated in the reflected light 61(s) by the segmented radial SLM 50. Inthis example, such selected portions 61(s) of the beam 27(p) represent,i.e., emanated largely from, details or features of the image 12′, suchas straight lines and short segments of curved lines, that alignlinearly with the angular orientation of the respective sectors 500,510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640,650 in which selected segments are located in the active optic area 54of the segmented radial SLM 50. For example, if one or more of thesegments 502, 504, 506, 508 in sector 500 is selected and activated torotate plane of polarization of light energy reflected from suchsegments(s), the reflected light energy 61(s) will have emanated largelyfrom details or features of the image 12′ that align linearly with thevertical orientation of the sector 500 in which segments 502, 504, 506,508 are positioned. Further, since the light energy 34 from higherspatial frequency content of the image 12′, e.g., closely spaced bumperand grill parts 35, are dispersed farther radially outward in theFourier transform optic pattern 32 than light energy 34 from lowerspatial frequency content, e.g., side panel 36, the light energy inreflected light beam 61(s) will also be characteristic of a confinedrange of such spatial frequency content of image 12′, depending on whichsegment of a sector is selected. For example, activation of outersegment 508 of sector 500 (FIG. 8), which is positioned farther radiallyoutward from the optical axis 40′ of the incident beam 27(p) thansegment 502, will cause the light energy in reflected beam 61(s) to becharacteristic of higher spatial frequency content of verticallyoriented features in image 12′, e.g., vertical edges of bumper and grillparts 35. In contrast, activation of inner segment 502 of sector 500,will cause the light energy in reflected beam 61(s) to be morecharacteristic lower spatial frequency content of vertically orientedfeatures in the image 12′, e.g., the vertical rear edge of the trunk lid37. The result is a filtered pattern 60 of light energy bands 62 thatrepresent or are characteristic of the unique combination of features orlines in the content of image 12′ that corresponds to light energy ofthe FT optic pattern 32 at the radial distance of the selected segment,sometimes called “scale”, and that align linearly with the sector inwhich the selected segment is positioned. Therefore, in addition tobeing able to provide rotational spatial filtering of the FT opticpattern 32 at different angular orientations about the optical axis, thesegments of each sector, such as segments 502, 504, 506, 508 of sector500, provided the additional capability of scalar spatial filtering FToptic pattern 32 at different radial distances from the optic axis.

Of course, segments in different sectors of different angularorientations about the optical axis 40 will align linearly with featuresor lines in the image 12′ that have different angular orientations, aswill be described in more detail below. Thus, the light energy bands 62in the filtered pattern 60 will change, as active optic segments indifferent sectors are selected and activated, to represent differentfeatures, details, edges, or lines in the optical pattern of image 12′at various angular orientations, intricateness or fineness, andbrightness, as will be explained in more detail below. In general,however, the light energy bands 62, if inverse Fourier transformed fromthe FT optic pattern 32 after the above-described spatial filtering 54,will be located in the same spatially-related sites as the features inthe original image 12′ from which such light energy emanated. Forexample, light energy in a band 62 in pattern 60 that originallyemanated from bumper and grill parts 35 in image 12′, after spatialfiltering with the vertical sector of the bumper and grill parts 35 inimage 12′.

The spatially filtered light energy in bands 62 of the filtered pattern60 can be detected by a photodetector 80 at any of the various angularorientations of the activated sectors and fed electronically to acomputer 20 or other microprocessor or computer for processing andencoding. While only one photodetector 80 with an example 16×16 array 82of individual photosensitive energy transducers 84 is illustrated inFIG. 1 and is sufficient for many purposes of this invention, otherdetector arrangements, for example, the two offset detector arraysdescribed in U.S. Pat. No. 6,678,411, or one or more larger detectorarrays, could also be used.

The computer 20, with input of information about the filtered opticalpatterns 60, i.e., light energy intensity (I) distribution, from thedetector array 82, along with information about the image 12 (e.g.,identification number, source locator, and the like), information aboutthe angular orientation (R) of the sector in which a segment isactivated, and information about the radial distance or scale (S) of theactivated segment relating to spatial frequency, can be programmed toencode the characteristics of the image 12 relating to the shape contentof the image 12. One useful format for encoding such information is bypixel of the filtered image 60, including information regarding x, ycoordinate location of each pixel, Rotation (i.e., angular orientationof the sector in which a segment is activated, thus of the linearfeatures of the image 12 that align with such angular orientation), andIntensity (i.e., amplitude of light energy from the filtered pattern 60that is detected at each pixel at the angular orientation R. Asearchable flag, such as a distortion factor X, can also be provided, asexplained, for example, in U.S. Pat. No. 6,678,411, or by a ghost imagepre-processing feature as explained, for example, in U.S. Pat. No.7,103,223. Such combination of angular orientation or rotation R, lightenergy intensity I for each pixel, and distortion factor X can be calleda “RIXel” for short. Scale (i.e., spatial frequencies of image 12content at such angular orientations) can also be included in suchencoding, if desired. When including a scale factor S, the combinationcan be called a “RIXSel”. Each RIXel or RIXSel can then be associatedwith some identifier for the image 12 from which it was derived (e.g., anumber, name, or the like), the source location of the image 12 (e.g.,Internet URL, data base file, book title, owner of the image 12, and thelike), and any other desired information about the image, such asformat, resolution, color, texture, content description, searchcategory, or the like. Some of such other information, such as color,texture, content description, and/or search category, can be informationinput from another data base, from human input, or even from anotheroptical characterizer that automatically characterizes the same image 12as to color, texture, or the like-whatever would be useful forsearching, finding, or retrieving image 12 or for comparing image 12 toother images.

Some, all, or additional combinations of such information about eachimage 12, 14 . . . , n characterized for shape and encoded, as describedabove, can be sent by the computer 20 to one or more data base(s) 102.Several example data base architectures 104, 106, 108 for storing RIXelor RIXSel information about each image 12, 14, . . . , n are shown inFIG. 1, but many other architectures and combinations of informationcould also be used.

The Fourier transform optic pattern 32, as mentioned above, issymmetrical from top to bottom and from left to right, so that eachsemicircle of the Fourier transform optic pattern 32 contains exactlythe same distribution and intensity of light energy as its oppositesemicircle. Light energy from lower spatial frequencies in the image 12′are distributed toward the center or optical axis 40′ of the Fouriertransform optic pattern 32, while the light energy from higher spatialfrequencies in the image 12′ are distributed farther away from theoptical axis 40′ and toward the outer edge of the pattern 32, i.e.,farther radially outward from the optical axis 40′. Light energy fromfeatures in the image 12′ that are distributed vertically in the image12′ to create those various spatial frequencies is likewise distributedvertically in the Fourier transform optic pattern 32. At the same time,light energy from features in the image 12′ that are distributedhorizontally in the image 12′ to create those various spatialfrequencies is distributed horizontally in the Fourier transform opticpattern 32. Therefore, in general, light energy from features in theimage 12′ that are distributed in any angular orientation with respectto the optical axis 40′ to create the various spatial frequencies in theimage 12′ is also distributed at those same angular orientations in theFourier transform optic pattern 32. Consequently, by detecting onlylight energy distributed at particular angular orientations with respectto the optical axis 40′ in the Fourier transform optic pattern 32, suchdetections are characteristic of features or details in the image 12′that are aligned linearly in such particular angular orientations. Theradial distributions of such detected light energy at each such angularorientation indicate the intricateness or sharpness of such linearfeatures or details in the image 12′, i.e., spatial frequency, while theintensities of such detected light energy indicate the brightness ofsuch features or details in the image 12′.

Therefore, a composite of light energy detections at all angularorientations in the Fourier transform optic pattern 32 creates acomposite record of the shapes, i.e., angular orientations,intricateness or sharpness, and brightness, of linear features thatcomprise the image 12′. However, for most practical needs, such as forencoding shape characteristics of images 12, 14, . . . , n for data basestoring, searching, retrieval, comparison and matching to other images,and the like, it is not necessary to record such light energy detectionsfor all angular orientations in the Fourier transform pattern 12′. It isusually sufficient to detect and record such light energy distributionsand intensities for just some of the angular orientations in the Fouriertransform optic pattern 32 to get enough shape characterization to bepractically unique to each image 12, 14, . . . , n for data basestorage, searching, and retrieval of such specific images 12, 14, . . ., n. For purposes of explanation, but not for limitation, use of11.25-degree angular increments is convenient and practical, becausethere are sixteen (16) 11.25-degree increments in 180 degrees ofrotation, which is sufficient characterization for most purposes and hasdata processing and data storage efficiencies, as explained in U.S. Pat.No. 6,678,411. However, other discrete angular increments could also beused, including constant increments or varying increments. Of course,varying increments would require more computer capacity and more complexsoftware to handle the data processing, storing, and searchingfunctions.

The segmented radial SLM 50, shown in FIG. 5, with its active opticsectors 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620,630, 640, 650 shown in FIG. 6, is used to select only light energy fromspecific angular orientations in the Fourier transform optic pattern 32for detection at any instant in time or increment of time on thedetector array 82. As explained above with reference to the sector 500in FIG. 7, which, except for angular orientation, is typical of all theother sectors 510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610,620, 630, 640, 650 in FIG. 6, any active optic segment, e.g., segments502, 504, 506, 508, in vertical sector 500, can be addressed viarespective electric traces, e.g., traces 503, 505, 507, 509 for sector500, so that the detector array 82 can detect light energy distributionand intensity (I) in the Fourier transform optic pattern 32 at anyangular orientation (R) of a sector 500, 510, 520, 530, 540, 550, 560,570, 580, 590, 600, 610, 620, 630, 640, 650 and at selected radialdistances from the optical axis 40′. For example, sector 500 is orientedsubstantially vertical in relation to the optical axis 40′. If all ofthe active optic segments 502, 504, 506, 508 of sector 500 are selectedand activated simultaneously, virtually all of the light energy that isdistributed vertically in the Fourier transform optic pattern 32 will beincident on, and detected by, the photodetector array 82 (FIG. 1).However, if only one of the active optic segments, for example, outersegment 508, is selected and activated, then only the light energy inthe Fourier transform optic pattern 32 that is distributed verticallyand the farthest radially outward from the optical axis 40 will bedetected by the photodetector array 82. Thus, any one, all, orcombination of the active optic segments, e.g., 502, 504, 506, 508, canbe activated sequentially or simultaneously to detect and record variousdistributions of light energy in the Fourier transform optic pattern 32.Also, any one or more sectors 500, 510, 520, 530, 540, 550, 560, 570,580, 590, 600, 610, 620, 630, 640, 650 can be selected and activatedsequentially, simultaneously, or in various combinations, depending onthe detail or particular light energy distributions in the FT opticpattern 32 it is desired to detect.

The preferred, but not essential, shape of the active optic sectors,e.g., sector 500, in the segmented radial SLM 50 is a narrow, elongatedwedge. The width of the wedge will depend on the light energy availableor needed and the optic resolution desired. A wider sector will directmore light energy 34 to the detector 80, but precision of line orfeature resolution of the image 12′ will degrade slightly. A narrowersector will get better line resolution, but with a correspondingincrease in the complexity of the resulting pattern shape generalizationand complexity and a decrease in light energy directed to the detector80. There may also be a practical limitation as to how narrow and closethe wedges can be made with the connecting electric traces in a limitedactive optic area 54 in an economic and efficient manner. Therefore, adesirable balance between these resolution, detectability, and sizeconsiderations may be struck in choosing sector size. Also, forspecialized applications, sectors of different shapes (not shown), suchas ovals, or other shapes could be used to capture shapes other thanlines from the image 12.

The number of active optic segments in a sector, e.g., the four segments502, 504, 506, 508 in sector 500, also has similar constraints. Smallersegments direct less light energy to the detector 80, but may providemore resolution of shape characteristics of the image 12′, whereaslarger segments direct more light to the detector 80, thus are moreeasily detectable, but resolution decreases. For lower resolutionapplications or requirements, the sectors may not even need to bedivided into segments, and this invention includes radial spatial lightmodulators in which each sector 500, 510, 520, 530, 540, 550, 560, 570,580, 590, 600, 610, 620, 630, 640, 650 is not segmented, thus comprisesa single active optic element for each sector. However, the same lowerresolution effect can be achieved in the illustrated embodiment 50 inFIGS. 5-7 by activating all the segments 502, 504, 506, 508 in a sectorsimultaneously, as described above.

In this example embodiment of SLM₂ 50, each sector, e.g., sector 500,comprises four individually addressable, active optic segments, e.g.,segments 502, 504, 506, 508, as shown in FIG. 7, although any number ofsegments other than four can also be used according to this invention.The length of each successive radial outward segment in this example istwice as long as the next adjacent radially inward segment. Thus, insector 500, the near inner segment 504 is about twice as long as theinner segment 502. Likewise, the near outer segment 506 is about twiceas long as the near inner segment 504, and the outer segment 508 isabout twice as long as the near outer segment 506. Expressed anotherway, if the radial length of inner segment 502 is L, the radial lengthof near inner segment 504 is 2L, the radial length of the near outersegment 506 is 4L, and the radial length of the outer segment 508 is 8L.The distance d between the optical axis 40′ and the inner edge 501 ofinner segment 502 is about the same as the length L of inner segment502, so the diameter of the center area 57 is about 2L. Theseproportional lengths of the active optic segments enable the innersegments (e.g., 502) to capture shape features of the image 12′ thathave sizes (in spatial frequency) in a range of about 25-50 percent ofthe size of the image 12′ produced by the spatial light modulator 26 inFIG. 5, the near inner segments (e.g., 504) to capture shape features ofthe image 12′ that have sizes in a range of about 25-50 percent of thesize of image 12′ produced by the spatial light modulator 26 in FIG. 5,the near outer segments (e.g., 504) to capture shape features of theimage 12′ that have sizes in a range of about 12½-25 percent of the sizeof image 12′, and the outer segments (e.g., 508) to capture shapefeatures of the image 12′ that have sizes in a range of about 3⅛-6¼percent of the size of the image 12′.

To illustrate, suppose the image 12′ is a pattern of a plurality ofparallel vertical lines intersecting a plurality of parallel horizontallines to form a matrix of squares, as illustrated, for example, in FIG.9 a or in FIG. 10 a. If the squares comprising the matrix are quitelarge, such as the squares 702 in FIG. 9 a, so that the vertical lines704, 706, which define the edges of the squares 702, are spaced farapart from each other by a distance equal to about 25-50 percent ofwidth of the whole image 12′, i.e., low spatial frequency, then thelight energy for that vertical shape content will be incident on theinner segment 502 of the vertical sector 500, as illustrated in FIG. 12.In contrast, if the squares of the matrix are quite small, such as thesquares 722 in FIG. 10, so that the vertical lines 724, which define theedges of the squares 722, are spaced closely together, such as by adistance equal to about 3⅛-6¼ percent of the width of the whole image12′, i.e., high spatial frequency, then the light energy for thatvertical shape content will be incident on the outer segment 508 of thevertical sector 500, as illustrated in FIG. 12. It follows, then, thatlight energy for the vertical shape content of a matrix ofintermediately sized squares (not shown) i.e., intermediate or moderatespatial frequency, would be incident on one or both of the intermediatesegments 504, 506 of the vertical section 500.

Also, light energy for the horizontal shape content of such large,small, or intermediate sized matrix square patterns would be incident onthe respective inner, outer, or intermediate positioned segments of thehorizontal sector 540. For example, in the image 12′ of FIG. 9 a withthe large squares 702, where the horizontal lines 706 are spaced apartby a distance equal to 25-50 percent of the width of the image 12′,i.e., low spatial frequency, the light energy for that horizontal shapecontent will be incident on the inner segment 542 of the horizontalsector 540, as illustrated in FIG. 12. In contrast, the example image12′ of small squares 722 in FIG. 10 a, wherein the horizontal lines 726are spaced apart by a distance equal to 3⅛-6¼ percent of the width ofthe image 12′, i.e., high spatial frequency, the light energy in the FTplane 32 for that horizontal shape content will be incident on the outersegment 548 of the horizontal sector 540, as illustrated in FIG. 12.

Further, any features of an image 12′ that have sizes over 50 percent ofthe size of image 12′, which light energy is incident on the center areaportion 41, can either be captured and detected as an indicator ofgeneral brightness of the image 12′ for intensity control or calibrationpurposes or just ignored and not captured or detected at all, becausethere is little, if any, useable shape information or content in thelight energy that comprises that 50 percent of the size of the image12′. Likewise, the approximately 3⅛ percent of the size content of theimage 12′ that is radially outward beyond the outer segments or sectorsis not detected and can be ignored in this preferred configuration. Thecenter 41 can be made optically active to capture light energy incidentthereon, if it is desired to capture and detect such light energy forgeneral brightness indication, intensity control, or calibrationpurposes, as will be understood and within the capabilities of personsskilled in the art. For example, if an image 12′ has a matrix ofsquares, which are so large that the distance between the verticallines, which define the edges of the large squares, is over 50 percentof the width of the image 12′, there is little, if any, vertical shapecontent of practical use, and the light energy for that vertical shapecontent is incident on the center area portion 41. On the opposite endof the spectrum, if such an image 12′ has a matrix of squares, which areso small that the distance between the vertical lines, which define theedges of the small squares, is less than about 3⅛ percent of the widthof the image 12′, there is also little, if any, vertical shape contentof practical use, and the light energy for such vertical shape contentis dispersed radially outward, beyond the outer segment 508 of sector500. Of course, other configurations or scale segment sizes andcombinations of the segmented radial SLM 50 could also be made and usedwithin the scope of this invention.

The shape content detection will be described in more detail below byuse of the example automobile image 12′ of FIG. 1. However, it ishelpful to understand at this point that, when the image 12′ is a matrixof squares, as described above, and when the light energy incident onthe vertical sector 500 in the Fourier transform plane 32 is projectedback into a spatial domain image 60, such spatial domain image 60 willhave been filtered to show only the vertical lines at the boundaries ofthe squares. No horizontal lines would appear in such spatial domain,filtered image, because the light energy with the horizontal shapecontent would have been substantially blocked or filtered out of theimage. Further, if the squares of the matrix pattern are large, such asthe squares 702 in FIG. 9 a described above, the vertical lines 704 ofsuch large squares 702 would only be re-formed and visible in thespatial domain, if the light energy incident on the near center segment502 of vertical sector 500 is actuated in a manner that does not blocksuch incident light energy in the Fourier transform plane, but, instead,allows it to project back into the spatial domain. In other words,actuation of the inner segment 502 of vertical sector 500 would projectthat incident light energy back into the spatial domain to re-form thevertical line 704 portions of that large square 702 image, asillustrated in FIG. 9 b. At the same time, actuating the outer segment508 to pass and not block or filter out light would not project verticallines to re-form in the spatial domain, because such low spatialfrequency light energy from a pattern of such large squares 702 is notdispersed radially outward enough to be incident on such outer segment508. Therefore, when there is a pattern of large squares 702 in theimage 12′, as illustrated in FIG. 9 a, actuation of any segment of thevertical sector 500, other than the inner segment 502, would not resultin the re-formed spatial image of the vertical lines 704 in FIG. 9 b,but would instead result in a blank, i.e., no spatial image, asillustrated in FIG. 11.

On the other hand, if the image 12′ has a matrix of very small squares722, thus high spatial frequency, as shown in FIG. 10 a and describedabove, then the light energy in the FT plane 32 is dispersed fartherradially outward to be incident on the outer segment 508 and not on theinner segment 502. Therefore, the outer segment 508 of vertical sector500 would have to be actuated to project such light energy of thevertical lines 724 of FIG. 10 a back into the spatial domain to displaythe vertical lines 724, as illustrated in FIG. 10 b. Further, actuationof the inner segment 502 would not project such vertical lines 724 inthe spatial domain, since there would be no light energy incident onsuch inner segment 502 in that case. Similar results for horizontallines 706 of FIG. 9 a and 726 of FIG. 10 a would be obtained from theseveral segments 542, 548 of the horizontal sector 540, as illustratedin FIGS. 9 b and 10 b.

In summary, for an image 12′ comprising a matrix of squares, asdescribed above, actuation of the inner segment 502 of vertical sector500 and getting vertical lines formed in the spatial domain, whileactuation of the outer segment 508 as well as the intermediate segments504, 506, in the vertical sector 500 projects no vertical lines in thespatial domain, would show that the vertical shape content of the imagehas low spatial frequency characteristic of large squares 702 in FIG. 9a. Similar analysis with the horizontal sector 540 resulting inhorizontal lines in the spatial domain from actuation of the innersegment 542, but not from actuation of the outer or intermediatesegments 548, 546, 544, would show such horizontal lines 706 to also below spatial frequency characteristic of large squares 702.

If analysis of other non-vertical and non-horizontal sectors 510, 520,530, 550, 560, 580, 590, 600, 610, 620, 630, 640, 650 show no lines inthe spatial domain from those angular orientations, then the recordableresults confirm the shape content of the image 12′ to be only a smalleror larger spatial frequency at some or all of those angularorientations, then the recordable results would confirm some shapecomplexity in addition to the matrix of squares in the image 12′. Thus,shape information, including spatial frequency or scale (S), andintensity (I) at each angular orientation or rotation (R) can beacquired with the spatial light modulator 50 in the system of thisinvention.

In summary, for an image 12′ with the large square 702 matrix shown inFIG. 9 a, the low spatial frequency vertical line 704 shape content ofthat image can only be projected from the FT plane 32 back into thespatial domain illustrated in FIG. 9 b by actuation of the inner segment502 of the vertical sector 500 in FIG. 12. Likewise, the low spatialfrequency horizontal line 706 shape content of that large square matriximage can only be projected from the FT plane 32 back into the spatialdomain illustrated in FIG. 9 c by actuation of the inner segment 542 ofhorizontal sector 540. Actuation of any other segment of sectors 500,510, 520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640 forthat large square, low spatial frequency, image 12′ of FIG. 9 a willresult only in a blank, as illustrated in FIG. 11, because, with thatkind of low spatial frequency image 12′ having only vertical andhorizontal lines, there will be no light energy incident on such othersegments. Actually, in practice, there could be some amount ofspill-over of light energy incident on some of such other segments,since the optical components and even the physical systems, can seldombe perfect. However, in a simple square grid image, such as shown inFIGS. 9 a and 10 a, such spill-over of light energy to adjacent segmentsand/or sectors would not usually be significant. More complex shapecontent in images could very well cause light energy in the FT plane 32to be incident on one or more adjacent segments and/or sectors atdifferent rotational (R) and radial (S) positions, in which case theintensities (I) of light on any such adjacent segments and/or sectorswould become part of the RIXSel information or shape data for such animage.

As illustrated in FIG. 8, the optic active segments 506, 508, which aretypical of other active optic segments, are part of an integratedcircuit 52, which is mounted on a chip base or platform 56. Theintegrated circuit 52 has a variable birefringent material 180, such asa liquid crystal material, sandwiched between two transparent substrates182, 184, such as high quality glass. The variable birefringent material180 is responsive to a voltage to change its birefringence in the areaof the voltage, which results in rotation of the plane of polarizationof the light that passes through the material 180. The division betweennear outer segment 506 and outer segment 508 is made by a separation ofrespective metal layers 186, 188. An intervening dielectric orelectrical insulation material 185 can be used to maintain electricalseparation of these metal layers 186, 188. As shown by a combination ofFIGS. 7 and 8, electrically conductive trace 507 is connected to themetal layer 186 of near outer segment 506, and trace 509 is connected tothe metal layer 188 of outer segment 508. In fact, the electric traces507, 509 and metal layers 186, 188 can be deposited on the same metaland can be on the back substrate 184 concurrently with their respectivemetal layers 186, 188 during fabrication of the integrated circuit 52,as would be understood and within the capabilities of persons skilled inthe art of designing and fabricating spatial light modulators, once theyare informed of the principles of this invention. Therefore, the metallayers 186, 188 can be addressed individually through their respectiveconnected traces 507, 509 by connecting positive (+) or negative (−)voltages V₁ and V₂, respectively, to traces 507, 509.

A transparent conductive layer 190 deposited on the front substrate 182is connected by another lead 513 to another voltage V₃. Therefore, avoltage can be applied across the portion of the liquid crystal material180 that is sandwiched between the metal layer 186 and the transparentconductive layer 190 by, for example, making V₁ positive and V₃ negativeand vice versa. Likewise, when a voltage can be applied across theportion of the liquid crystal material 180 that is sandwiched betweenthe metal layer 188 and the transparent conductive layer 190 by, forexample, making V₂ positive and V₃ negative and vice versa.

As mentioned above, the function of the respective segments 506, 508 isto rotate the plane of polarization of selective portions of theincident light beam 27(p) so that those portions of the light beam27(p), which carry corresponding portions of the Fourier transform opticpattern 32, can be separated and isolated from the remainder of thelight beam 27(p) for detection by the photodetector array 82 (FIG. 1).As understood by persons skilled in the art, there are a number ofspatial light modulator variations, structures, and materials that canyield the desired functional results, some of which have advantagesand/or disadvantages over others, such as switching speeds, lighttransmission efficiencies, costs, and the like, and many of which wouldbe readily available and satisfactory for use in this invention.Therefore, for purposes of explanation, but not for limitation, thesegmented radially spatial light modulator illustrated in FIG. 8 canhave respective alignment layers 192, 194 deposited on the transparentconductive layer 190 on substrate 182 and on the metal layers 186, 188on substrate 184. These alignment layers 192, 194 are brushed orpolished in a direction desired for boundary layer crystal alignment,depending on the type of liquid crystal material 180 used, as iswell-understood in the art. See, e.g., J. Goodman, “Introduction toFourier Optics, 2^(nd) ed., chapter 7 (The McGraw Hill Companies, Inc.)1996. An antireflective layer 196 can be deposited on the outsidesurface of the glass substrate 182 to maintain optical transmissiveefficiency.

One example system, but certainly not the only one, can use a liquidcrystal material 180 that transmits light 27(p) without affectingpolarization when there is a sufficient voltage across the liquidcrystal material 180 and to act as a ¼-wave retarder when there is novoltage across the liquid crystal material. An untwisted crystalmaterial 180 that is birefringent in its untwisted state can function inthis manner. Thus, for example, when no voltage is applied across theliquid crystal material 180 in segment 508, there is no molecularrotation of the liquid crystal material 180 in outer segment 508, andthe liquid crystal material in outer segment 108, with the properthickness according to the liquid crystal manufacturer's specifications,will function as a ¼-wave plate to convert p-polarized light 27(p)incident on outer segment 508 to circular polarization as the lightpasses through the untwisted liquid crystal material 180. Upon reachingthe metal layer 188, which is reflective, the light is reflected andpasses back through the liquid crystal material to undergo another¼-wave retardation to convert the circular polarization to linearpolarization, but in the s-plane, which is orthogonal to the p-plane.The reflected light 61(s), therefore, has its plane of polarizationeffectively rotated by 90 degrees in relation to the incident light27(p).

Meanwhile, if there is a sufficient voltage on, for example, the nearouter segment 506, to rotate the long axes of the liquid crystalmolecules into alignment with the direction of propagation of theincident light waves 27(p), thereby eliminating the birefringence of theliquid crystal material 180, then there is no change of the linearpolarization of the light on either its first pass through the liquidcrystal material 180 or on its second pass through the liquid crystalmaterial after being reflected by metal layer 186. Consequently, underthis condition with a voltage applied across the liquid material 180 innear outer segment 506, the reflected light 61(p) is still polarized inthe p-plane, i.e., the same plane as the incident light 27(p).

Many liquid crystal materials require an average DC voltage bias ofzero, which can be provided by driving the voltage V₃ with a square wavefunction of alternating positive and negative voltages for equal times.Therefore, for no voltage across the liquid crystal material 180, theother voltages V₁, V₂, etc., can be driven in phase with equal voltagesas V₃. However, to apply a voltage across the liquid crystal material180 adjacent a particular metal layer 186, 188, etc., to activate thatparticular segment 506, 508, etc., as described above, the respectivevoltage V₁ or V₂, etc., can be driven out of phase with V₃. If thefrequency of the square wave function is coordinated with the switchingspeed of the liquid crystal material 180, one-half cycle out of phasefor a voltage V₁, V₂, etc., will be enough to activate the liquidcrystal material 180 to rotate the plane of polarization of the light asdescribed above.

As mentioned above, other alternate arrangements and known liquidcrystal materials can reverse the results from an applied voltage. Forexample, a twisted liquid crystal material 180 may be used to rotateplane of polarization under a voltage and to not affect plane ofpolarization when there is no voltage.

Referring again primarily to FIG. 1 with continuing secondary referenceto FIG. 4, the light energy in the beam 27(p), which passes through thepolarizer/analyzer 116 is focused as the Fourier transform optic pattern32 on the SLM₂ 50. Selected active optic segments, for example, segments502, 504, 506, 508, in the SLM₂ 50, can rotate the plane of polarizationof portions of the incident light beam 27(p), as described above, inorder to separate and isolate light energy from selected portions of theFT optic pattern 32 for detection by photodetector 80. The computer 20can be programmed to provide signals via link 198 to the SLM₂ 50 toselect and coordinate activation of particular segments, for example,segments 502, 504, 506, 508, with displays of particular images 12, 14,. . . , n. The computer 20 can also be programmed to coordinate lasersource 23 via a link 29 to produce the required light energy 24, whenthe selected segment of the SLM₂ 50 is activated.

Instead, the s-polarized light 61(s) is reflected by the mirror 806 tothe detector 80 in the spatial domain. The lens 78 projects the filteredimage 12′ via the isolated beam 61(s) in a desired size in the spatialdomain on the detector array 82 of photodetector 80.

The photodetector array 82, as mentioned above, can be a 16×16 array ofindividual light sensors 84, such as charge coupled devices (CCDs), asshown in FIG. 1, or any of a variety of other sizes and configurations.The x, y coordinates of individual sensors 84 in the array 82 thatdetect light 61(s) can be communicated, along with light intensity (I)information, to the computer 20 or other controller or recording devicevia a link 86, where it can be associated with information bout theimage 12, 14, . . . , n and the angular orientation (R) and/or radialposition (S) of the activated segment(s) in the segmented radial SLM 50that provided the beam 61(s) to the detector 80.

The spatial filtering process described above and its characterizationof the image 12 by shape content is illustrated in more detail in FIGS.13 a-c, 14 a-c, 15 a-c, 16 a-c, and 17 a-c. With reference first to FIG.13 a, the active optic area 54 from FIGS. 5 and 6 is shown in FIG. 13 awith the example sectors 500, 510, 520, 530, 540, 550, 560, 570, 580,590, 600, 610, 620, 630, 640, 650, but, to avoid unnecessary clutter,without the electric traces that were described above and shown in FIGS.5-7. As mentioned above, the sectors can be any desired width or anydesired angular orientation, but a convenient, efficient, and effectiveconfiguration is to provide sectors of 11.25°. For example, a circle of360° divides into 32 sectors of 11.25° each, and a semicircle of 180°divides into sixteen sectors of 11.25° each. Further, as mentionedabove, the light energy distribution in any semicircle of a Fouriertransform optic pattern 32 is symmetric with its opposite semicircle.Therefore, in accordance with this symmetry principle, detection of thelight energy pattern in one semicircle of the FT optic pattern 32, forexample, in the semicircle extending from 0° to 180°, provides effectiveinformation for the entire image 12′, and detection of the light energypattern in the opposite semicircle extending from 180° to 360° providesthe same information. Consequently, to alleviate clutter and betteraccommodate the electric traces (shown in FIGS. 5-7, some of sectors canbe positioned in one semi-circle of the optic area 54 with interveningspaces to accommodate the electric traces (shown in FIGS. 5-7), whileothers of the sectors can be positioned in the opposite semicircle ofthe optic area 54 diametrically opposite to the intervening spaces. Forexample, when the circle is divided into 32 sectors of 11.25° each, only16 of those sectors, such as sectors 500, 510, 520, 530, 540, 550, 560,570, 580, 590, 600, 610, 620, 630, 640, 650 have to be optically activeto detect all of the shape content in the light energy incident on thearea 54. All 16 of such optically active sectors could be positioned inone semicircle of the area 54, or, as explained above, it is moreconvenient and less cluttered to position some of the optically activesectors in one semicircle with intervening spaces and others in theopposite semicircle diametrically opposite to the intervening spaces. Inthe example of FIG. 10 a, any eight of the sectors, e.g., sectors 640,650, 500, 510, 520, 530, 540, 550, separated by non-active areas 641,651, 501, 511, 521, 531, 541, are positioned in one semicircle of thearea 54, while the remaining eight of the sectors 560, 570, 580, 590,600, 610, 620, 630, also separated by non-active areas 561, 571, 581,591, 601, 611, 621, can be positioned in the opposite semicircle, asshown in FIG. 13 a. When each of the 16 active optic sectors 500, 510,520, 530, 540, 550, 560, 570, 580, 590, 600, 610, 620, 630, 640, 650 inthis arrangement is positioned diametrically opposite a non-active area,the symmetry of the FT optic pattern 32 (FIG. 1) effectively allows allof the shape content in the light energy distribution in FT opticpattern 32 to be detected with these sectors—bit including, of course,the light energy incident on the center area portion 41 or that isdispersed radially outward beyond the outer segments, which has little,if any, significant shape content, as explained above.

This principle also facilitates design and fabrication of an effectivespatial filtering SLM₂ 50, because, for every active optic sector, therecan be an adjacent inactive sector or area available for placement ofelectrically conductive traces to the segments, as shown by referenceback to FIGS. 6 and 7. For example, the inactive area 651 between activeoptic segments 500 and 650 accommodates placement of traces 503, 505,and 507 (shown in FIG. 7) to respective segments 502, 504, 506 of activeoptic sector 500. To provide active optic sectors to detect light energyincident on the non-active areas, for example, the non-active area 501in FIG. 13 a between active optic sectors 500, 510, the above-describedsymmetry principle is applied by providing an active optic sector 590 ina position diametrically opposite the said non-active area 501.Therefore, detection of light energy detected in the active optic sector590 is effectively detecting light energy incident on the non-activearea 501 between sectors 500, 510. In order to have an active opticsector positioned diametrically opposite a non-active area, two of theactive optic sectors, e.g., sectors 550, 560 are positioned adjacenteach other without any significant intervening non-active area, so thediametrically opposite non-active area 631 is twice as big as othernon-active areas. Therefore, according to the above-described symmetryprinciple, substantially all shape content in the light energy 34 of FToptic pattern 32 (FIG. 1) is detectable by the sixteen 11.25° activeoptic sectors 500, 510, 520, 530, 540, 550, 560, 570, 580, 590, 600,610, 620, 630, 640, 650.

Returning now to FIG. 13 a, vertical angular orientation is arbitrarilydesignated as 0°, so horizontal angular orientation is at 90°. Eachactive optic sector 500, 510, 520, 530, 540, 550, 560, 570, 580, 590,600, 610, 620, 630, 640, 650 is about 11.25°. Active optic sectors fromsector 640 clockwise to sector 550 are each separated by respectivenon-active areas 641, 651, 501, 511, 521, 531, 541 of 11.25°. Therefore,each active optic sector from sector 560 clockwise to sector 630 ispositioned diametrically opposite a respective non-active area 561, 571,581, 591, 601, 611, 621. Consequently, substantially all the shapecontent in the light energy distribution in the FT optic pattern 32(FIG. 8) incident on the active area 54 can be detected in 11.25°intervals by the 11.25° sectors 500, 510, 520, 503, 504, 550, 560, 570,580, 590, 600, 610, 620, 630, 640, 650 positioned as described above.

For example, shape content in the light energy characteristic of thatincident on both the vertical 11.25° sector 500 centered at 0° as wellas on the non-active area 581 centered at 180° can be detected byeffectively activating the active optical segments 502, 504, 506, 508 ofsector 500. Shape content in the light energy characteristic of thatincident on the 11.25° sector 590 centered at 191.25° as well as on thenon-active area 501 centered at 11.25° can be detected effectively byactivating the active optic segments of sector 590, because the activeoptic sector 590 is centered diametrically opposite the non-active areaof 11.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 510 centered at 22.5° or thenon-active area 591 centered at 202.5° can be detected by activating theactive optic segments of sector 510. Shape content in the light energycharacteristic of that incident on either the 11.25° non-active areacentered at 33.75° or active sector 600 centered at 213.75° can bedetected by activating the active optic segments of sector 600, which iscentered diametrically opposite 33.75° at 213.75°. Shape content in thelight energy characteristic of that incident on either the 11.25° sector520 centered at 45° or non-active area 601 centered at 225° can bedetected by activating the active optic segments of sector 520. Shapecontent in the light energy characteristic of that incident on eitherthe 11.25° non-active area 521 centered at 56.25° or the active sector610 centered at 236.25° can be detected by activating the active opticsegments of sector 610, which is centered diametrically opposite 56.25°at 256.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 530 centered at 67.5° or thenon-active area 611 centered at 247.5° can be detected by activating theactive optic segments of sector 530. Shape content in the light energycharacteristic of that incident on either the 11.25° non-active area 531centered at 78.75° or active sector 620 centered at 258.75° can bedetected by activating the active optic segments of sector 620, which iscentered diametrically opposite 78.75° at 258.75°. Shape content in thelight energy characteristic of that incident on either the 11.25° sector540 centered at 90° or non-active area 621 centered at 270° can bedetected by activating the active optic segments of sector 540. Shapecontent in the light energy characteristic of that incident on eitherthe 11.25° non-active area 541 centered at 101.25° or the active sector630 centered at 281.25° can be detected by activating the active opticsegments of sector 630, which is centered diametrically opposite 101.25°at 281.25°. Shape content in the light energy characteristic of thatincident on either the 11.25° sector 550 centered at 112.5° thediametrically opposite portion of non-active area 631 that is centeredat 292.5° can be detected by activating the active optic segments ofsector 550. Shape content in the light energy characteristic of thatincident on the 11.25° sector 560 centered at 123.75°. The diametricallyopposite portion of non-active area 631 that is centered at 303.75° canbe detected by activating the active optic segments of sector 560. Shapecontent in the light energy characteristic of that incident on the11.25° non-active area 561 centered at 135° or active sector 640centered at 315° can be detected by activating the active optic segmentsof sector 640, which is centered diametrically opposite 135° at 315°.Shape content in the light energy characteristic of that incident on the11.25° sector 570 centered at 146.25° or non-active area 641 centered at326.25° can be detected by activating the active optic segments ofsector 570. Shape content in the light energy characteristic of thatincident on the 11.25° non-active area 571 centered at 157.5° or activesector 650 centered at 337.5° can be detected by activating the activeoptic segments of sector 650, which is centered diametrically opposite157.5° at 337.5°. Finally, shape content in the light energycharacteristic of that incident on the 11.25° sectors 580 centered at168.75° or non-active area 651 centered at 348.75° can be detected byactivating the active optic segments of sector 580.

While it would be unnecessarily cumbersome to illustrate and describethe shape detecting and characterizing functionality of all the activeoptic segments of all the sectors 500, 510, 520, 530, 540, 550, 560,570, 580, 590, 600, 610, 620, 630, 640, 650, it may be helpful toillustrate and describe the functionality and results of activatingseveral representative examples of the active optic segments in theactive optic area 54. Therefore, FIG. 13 a illustrates activation of theouter segment 508 of the active optic sector 500 by depicting bands oflight energy 34 from the FT optic pattern 32 that are incident on andreflected by the outer segment 508. These bands of light energy 34,which are dispersed farthest radially outward in the vertical directionin the FT optic pattern 32, emanated originally from, and correspond to,substantially vertically oriented lines, edges, features, or details inthe image 12′ that have a higher spatial frequency, such as thesubstantially vertical lines of the bumper and grill parts 35 in FIG. 13b. As explained above, the light energy 34 from the more intricate orclosely spaced vertical parts or lines 66 (i.e., higher spatialfrequency), such as those in the front bumper and grill portion 35 ofthe automobile in image 12′, are dispersed farther radially outward fromthe optical center or axis 40′, thus detectable by activating outersegments 506, 508 of vertical sector 500, while the light energy 34 fromthe less intricate, more isolated and semi-isolated or farther spacedapart vertical parts, edges, or lines (i.e., lower spatial frequency),such as the substantially vertical parts or lines 66′ in the trunk andrear bumper portions of the image 12′ in FIG. 13 b, are dispersed not sofar radially from the optical center or axis 40 and would be moredetectable by inner segments 502, 504. The intensity of the light energy34 in those respective dispersion bands, as explained above, depends onthe brightness of the corresponding respective vertical features 35, 66,66′ in the image 12′. Again, the central portion 41 of the active opticarea 54 can be ignored, if desired, because the light energy 54 in andnear the center or axis 40 of the Fourier transform 32 (FIG. 1) emanatesfrom features in image 12′ with very low or virtually no spatialfrequencies, such as the overall brightness of the image, which do verylittle, if anything, to define shapes. On the other hand, as alsoexplained above, the center portion 41 can be fabricated as an activeoptic component to capture and reflect the light energy incident on thecenter portion 41 to the detector 80 as a measure of overall brightness,which may be useful in calibrating, adjusting brightness of the sourcelight 25(s) (FIG. 1), calibrating intensity (I) measurements of sensors84 in detector 80, and the like.

The light energy bands 34, when reflected by the activated outer segment508, are filtered through the polarizing beam splitter 70 and projectedin the filtered optic pattern 60, which is comprised primary of verticallines or bands 62 of light energy illustrated diagrammatically in FIG. 9c, to the photodetector 80 (FIG. 1). As discussed above, the lightenergy in the filtered optic pattern 60 is detected by the light sensors84 in detector array 82. The intensity (I) of light energy on eachsensor 84 is recorded along with the sensor (pixel) location, preferablyby x-y coordinates, and the angular orientation (R) of the sector 500.The radial position or scale (S) of the activated segment 508(indicative of spatial frequency, as described above) is also recorded,for example, as RIXSel values described above. These values can bestored in a database 102 in association with information about thecharacterized image 12, such as image identification (ID), sourcelocation (URL, database address, etc.) of the image 12, digital format,resolution, colors, texture, shape, subject matter category, and thelike.

To illustrate further, the near inner segment 504 of active optic sector500 is shown in FIG. 14 a as being selected to rotate plane ofpolarization of selected portions of the light energy bands 34 from theFT optic pattern 32 for isolation by the polarizer/analyzer 70 and thendetection by the photodetector 80. This near inner segment 504 is alsoin the vertically oriented sector 500, but it is positioned or scaledradially closer to the optical axis 40′ than the outer segment 508,which was activated in the previous example. Therefore, this near innersegment 504, when activated, captures light energy 34 in the FT opticpattern 32 that also corresponds to vertical lines, edges, etc., of theimage 12′, but to such lines, edges, etc., of lesser spatial frequencythan those selected by the outer segment 508. For example, instead ofthe closely spaced, vertically oriented bumper and grill parts 35, thelight energy 34 from the FT optic pattern 32 selected by the near innersegment 504 may be more characteristic of the more spatiallysemi-isolated, vertical edge 66′ of the trunk lid and other verticallines and edges 66 of similar semi-isolation in the automobile image 12′in FIG. 13 b. Therefore, the light energy bands 62 in the resultingfiltered beam 61(s), as shown in optic pattern 60 in FIG. 15 c, arecharacteristic of such vertical shape content 66, 66′ of lower spatialfrequency in the image 12′.

Another example angular orientation of light energy 34 from the FT opticpattern 32 is illustrated by FIGS. 15 a-c. The near outer segment 526 inthis example is activated to capture light from lines, edges, orfeatures extending radially at an angular orientation of 45° fromvertical. Such light energy 34 is characteristic of lines, edges, orfeatures in the image 12′ that extend at about 45° and that have somespatial frequency, i.e., are not isolated, such as, perhaps, the windowpost and roof support 67 in FIG. 15 b. Such 45° oriented lines in theimage 12′ with even less spatial frequency, i.e., even more isolated,for example, the portions of the fender and hood edges 67′, might becaptured more by the near inner segment 524 or inner segment 522,although it is possible that some of such light energy could also becaptured by near outer segment 506. The filtered beam 61(s) with theoptical pattern 60 for these 45° angular oriented shape contents havebands 62 of the light energy oriented at about 45°, as illustrateddiagrammatically in FIG. 15 c. Such light energy bands 62 are detectedby sensors 84 for photodetector 80 (FIG. 1) and are recorded and storedas characteristic of the spatial frequency of 45°-oriented shape contentof the image 12′.

Capture and detection of horizontal portions of lines, edges, andfeatures 68, 68′ of the image 12′ of respective spatial frequencies, ifpresent in the image 12′, is accomplished by activation of one or moresegments 542, 544, 546, 548 of horizontal sector 540, which is oriented90° from the vertical 0°. The portion of the light energy 34 that isreflected by each activated segments 542, 544, 546, 548 of thehorizontal sector 540 is characteristic of all of the substantiallyhorizontal features, parts, and lines 68 of the respective spatialfrequencies in the image 12′ that correspond to the light energy, ifany, that is incident on those segments in the FT plane 32, as shown inFIG. 16 b. Some curved features, parts, or lines in the image 12′ haveportions or line segments 68′ that are also substantially horizontal, sothose horizontal portions or line segments 68′ also contribute to thelight energy 34 that gets reflected by the horizontal sector 540 in FIG.16 a. The bands 62 of light energy in the filtered pattern 60, shown inFIG. 16 c, resulting from the horizontal orientation of an activatedsegments 542, 544, 546, 548 in FIG. 16 a, are also orientedsubstantially horizontal and are indicative of some or all of the shapecharacteristics 68, 68′ of image 12′ that are oriented substantiallyhorizontal. Again, the inner segments 542, 544 are activated to detectlight energy bands 34 from the FT optic pattern 32 that are dispersedcloser to the optical axis 40′, thus are characteristic of lower spatialfrequency, horizontal shape content of the image 12′, while higherspatial frequency, horizontal shape content can be detected byactivating the outer segments 546, 548 of the horizontal sector 540.Thus, detection of the light energy bands 62 in FIG. 13 c by detectorarray 82 (FIG. 1) facilitates encoding and recording of the horizontalshape characteristics of the image 12′, as was described above.

One more example activated segment 598 in sector 590, is illustrated inFIG. 17 a to describe the symmetric light energy detection featuredescribed above. As explained above, the light energy bands 34 of the FToptic pattern 32 that are incident on the non-active area between theactive optic sectors 500, 510 are symmetric with the diametricallyopposite light energy bands 34, which are incident on the active opticsegments 529, 594, 569, 598 in sector 590. Therefore, activation of asegment, for example, outer segment 598, as illustrated in FIG. 17 a,will enable effective detection of the same shape content as is in thediametrically opposite, equivalent light energy 34, which is incidentbetween the segments 508, 518 of respective sectors 500, 510. Likewise,activation of any other segment 592, 594, 596 enables effectivedetection of shape content in the other diametrically opposite portionsof light energy that is incident in the non-active area 501 betweenactive sectors 500 and 510. Therefore, detecting light energy 34incident on the sector 590, which is centered at 191.25° in the exampleof FIG. 17 a, is the equivalent of detecting light energy 34 that isincident on the non-active area 501 centered at 11.25°. The oppositealso holds, i.e., detection of light energy 34 incident on the verticalsector 500, as illustrated in FIGS. 9 a and 10 a and described above, isthe equivalent to detecting light energy from the FT optic pattern 32that is incident on the non-active area 581 between active sectors 580and 590.

Referring again to FIGS. 17 a-c, the light energy 34 detected in thesector 590 corresponds to shape content 69, such as lines, edges,portions of curves, and the like in the image 12′ that are orientedsubstantially at about 191.25°, which, being symmetrical, can also beexpressed as oriented at about 11.25°. The light energy bands 62 in thereflected and filtered optic pattern 60 also have that same angularorientation, which is characteristic of the linear shape content of theimage 12′ that has that angular orientation and that has higher spatialfrequency if reflected by outer segments 596, 598 or lower spatialfrequency if reflected by inner segments 592, 594. the optic patterns 60resulting from such various reflected portions of the FT optic pattern32 are detected by the sensors 84 in detector array 82 for recording andstorage, as described above.

It should be clear by now that any particular angular orientation R ofsegments of sectors in the active optic area 54 will allow detection ofall the shape characteristics of image 12′ that have substantially thatsame angular orientation R. It should also be clear that radial outwardspacing or scale (S) of the segments relates to spatial frequency ofsuch shape characteristics. Thus, all of the shape characteristics ofthe image 12′ can be detected by detecting the bands 62 of therespective filtered patterns 60 with the segments at all angularorientations. However, as mentioned above, it is sufficient for mostpurposes to detect some, preferably most, but not necessarily all, ofthe shape characteristics of the image 12′ by choosing to detect thelight energy bands 34 of filtered patterns 60 at certain selectedincrements of angular orientation or rotation R. Obviously, the biggerthe increments of angular orientation of the sectors where light energybands 34 are detected, the less precise the detected shapecharacteristics or contents of the image 12′ will be. On the other hand,the smaller the increments of angular orientation, the more data thatwill have to be processed. Therefore, when selecting the angularincrements of sectors at which light energy bands 34 will be detectedand recorded, it may be desirable to strike some balance betweenpreciseness of shape characteristics needed or wanted and the speed andefficiency of data processing and storage required to handle suchpreciseness. For example, but not for limitation, it is believed thatdetection and recording of the shape characteristics at angularincrements of in a range of about 5 to 20 degrees, preferably about11.25-degrees, will be adequate for most purposes. Also, the angulararea of detection can be varied. For example, even if active opticsectors are oriented to detect shape characteristics at angularincrements of 11.25°, the active optic areas could be narrow, such as ina range of 3° to 8°, more or less, which would filter out some of theoptic energy from the FT optic pattern 32 between the sectors. However,such loss of light energy from non-active areas between sectors or otherradially extending sensors, as described elsewhere in thisspecification, may not be detrimental to shape characterization by thisinvention, depending on specific applications of the technology toparticular problems or goals.

Instead of the radially extending, wedge-shaped active optic sectors andsegments of sectors described above, an alternate configuration can becomprised of radially extending, rectangular-shaped active opticmodulators as illustrated diagrammatically in FIG. 18. Theserectangular-shaped modulators 500′, 510′, 520′, 530′, 540′, 550′, 560′,570′, 580′, 590′, 600′, 610′, 620′, 630′, 640′, 650′ can be at the sameor different angular orientations as the wedge-shaped sectors describedabove, and each angular orientation can comprise several rectangular,active optic segments, such as segments 502′, 504′, 506′, 508′ of themodulator 500′. This arrangement does not capture as much of the lightenergy of an incident FT optic pattern 32 (FIG. 1) as the wedge-shapedsegments and sectors described above, but shape resolution may begreater.

Another, albeit less efficient embodiment, is illustrated in FIG. 19,where the desired sectors and segments, which are shown in phantomlines, can be formed by activating selected groups of light modulatorelements 732 in a pixel array 730 type of spatial light modulatorsimultaneously. For example, a virtual outer segment 508″ of a verticalsector 500″ can be activated by activating simultaneously a segmentgroup 508″ of the light modulator pixel elements 602.

While the reflective spatial light modulator structure described abovein connection with the cross-sectional view of FIG. 8 may be applicableto all of the SLM₂ 50 configurations described above, an alternative,transmissive, spatial light modulator structure 50′ illustrated in FIG.20 could also be used with each of the configurations, such as in theFIG. 2 example described above. In this embodiment 50′, the metalreflective layers 186, 188 are replaced by transparent conducting layers186′, 188′, such as indium tin oxide (ITO) or any of a number of otherwell-known transparent conducting materials. Therefore, incident 27(p)may or may not have its plane of polarization rotated, depending onwhether a voltage V is applied to either layer 186′ or 188′, but,instead of being reflected, the light is transmitted through the device50′ to emerge as light energy 61(s) or 61(p), as indicated in FIG. 17.This device is mounted around its periphery in a base 56, so the base 56does not interfere with the light 61(s) and 61(p) propagation. Adifferent liquid crystal material 180′ and/or a different thickness ofliquid crystal material than the liquid crystal material 180 for theFIG. 8 embodiment would be required, since the light passes only oncethrough the liquid crystal material 180′. However, such materials andtheir applications are readily available and well-known in the art andcan be implemented by persons skilled in the art, once they understandthe principles of this invention. Also, since the light 61(s) istransmitted rather than reflected, the polarizer/analyzer 70 would alsohave to be positioned behind the spatial filtering SLM 50′ of FIG. 17 asshown in FIG. 2 instead of in front of it.

In the description above, the shape content of a desired angularorientation (R) and scale (S) of an image is captured by masking orblocking all other light in the FT plane 32 from reaching the detector80 so that only the light energy from that angular orientation (R) andscale segment of the FT plane 32 gets projected back into the spatialdomain for detection. However, persons skilled in the art will recognizethat shape characterization and encoding with the components describedabove can also be practiced in the negative. In other words, instead ofactuating the one or several segments and/or sectors to get shapecontent relevant to the angular orientation or rotation (R) and/orradial distance (S) of particular sectors and/or segments, as describedabove, it would also be feasible to actuate all of the other sectors andsegments in the active optic area 54 and not actuate the specific sectorand/or segments in order to get a negative or inverse of the shapecontent of the image. This procedure can be repeated for all of thedesired angular (R) and/or scalar (S) sectors and segments so that thecomposite of information regarding light energy distribution collectedand recorded represents a negative or inverse of all of the shapecontent of an image 12′.

For example, referring back to FIGS. 9 a-c, the negative or inverse ofthe vertical shape content of FIG. 9 a in the spatial domain afteroptical filtering in the FT plane 32 by the spatial filtering SLM₂ 50(FIG. 1) would appear as the horizontal lines 706, similar to the waythey appear in FIG. 9 c, with the vertical lines 704 filtered out of thespatial image by the non-actuated inner segment 502 of vertical sector500. If there was more shape content than the squares in FIG. 9 a, thensuch additional shape content would also show in the negative spatialimages, as long as it would not be in the vertical orientation and inthe spatial frequency range that is filtered out of the image by theinner segment 502. Likewise, the negative or inverse of the horizontalshape content of FIG. 9 a in the spatial domain after optical filteringin the FT plane 32 by the segmented radial SLM 50 would appear as thevertical lines 704, similar to the way they appear in FIG. 9 b, with thehorizontal lines filtered out of the spatial image.

To explain further, a negative of the spatially filtered image 60 of theautomobile illustrated in FIG. 13 b would show all of the shape contentof the automobile, except the vertical lines 62′ shown in FIG. 13 c. Thesame differences would apply to negatives for FIGS. 14 c, 15 c, 16 c,and 17 c.

Again, as with the positive spatial images of the shape content, suchnegative or inverse spatial images can be detected at 80 (FIG. 1) bypixels at x-y coordinate locations and intensity (I) and processed forstorage with angular orientation (R) and, if desired, radial scale (S)of the non-actuated sectors and segments, as described above. Also,negative filtered image data can be converted to positive filtered imagedata and vice versa, as would be understood by persons skilled in theart.

While a number of example implementations, aspects, and embodiments havebeen described above, persons skilled in the art will recognize othermodifications, permutations, additions, and subcombinations that arewithin the scope and spirit of the claimed invention. Therefore, it isintended that the following claims and claims hereafter introduced areinterpreted and construed to include all such modifications, additions,and subcombinations and equivalents as are within their true spirit andscope, and to not limit such claims the exact construction and processshown and described above. The words “comprise,” “comprises,”“comprising,” “composed,” “composes,” “composing,” “include,”“including,” and “includes” when used in this specification and in thefollowing claims are intended to specify the presence of statedfeatures, integers, components, or steps, but they do not preclude thepresence or addition of one or more other features, integers,components, steps, or groups thereof.

1. Apparatus for processing an optical image isolating shape content andcharacterization of the optical image, comprising: a source of coherent,monochromatic light for propagating a beam of planar polarized,coherent, monochromatic light along a beam path; a first opticalsubsystem comprising a focusing lens positioned in the beam path andshaped to focus the beam to a focal point at a focal plane, an imageinput device positioned between the focusing lens and the focal point,wherein the image input device has the capability of modulating the beamof light with spatially dispersed phase changes that result indiffracted light of an image in the beam, and a spatial filterpositioned in the beam where a Fourier transform pattern of the image ispresented; and a second optical subsystem overlapping the first opticalsubsystem in the beam path comprising a projection lens havingrespective focal points at respective focal distances on opposite sidesof the projection lens, and a detector, wherein the second opticalsubsystem is optically coupled to the first optical subsystem with theprojection lens and both of the focal points of the projection lenspositioned on the beam path between the image input device and thedetector and with the spatial filter positioned optically between theimage input device and the projection lens.
 2. The apparatus of claim 1,wherein the image input device is positioned anywhere between thefocusing lens and the focal point where the beam illuminates the fullimage.
 3. The apparatus of claim 2, wherein the projection lens ispositioned anywhere between the spatial filter and the detector where itscales the image from the image input device to a desired size on thedetector.
 4. The apparatus of claim 2, wherein the image input deviceincludes a pixilated imaging spatial light modulator that modulatesphase of light in the beam on a pixel-by-pixel basis to rotate plane ofpolarization and diffract the light in a manner that writes the imageinto the beam.
 5. The apparatus of claim 4, including apolarizer/analyzer positioned between the imaging spatial lightmodulator and the spatial filter for separating pixels of lightpolarized indifferent planes to pass light comprising the image towardthe detector and remove from the beam light that is not part of theimage.
 6. The apparatus of claim 5, wherein the imaging spatial lightmodulator is a reflecting spatial light modulator in which the image iswritten into the beam by liquid crystal material adjacent a reflectionplane that reflects the light beam, and wherein the reflecting spatiallight modulator is oriented such that the beam has angle of incidence atthe imaging spatial light modulator reflection plane of more than zerodegrees.
 7. The apparatus of claim 6, wherein the angle of incidence ofthe beam at the imaging spatial light modulator reflection plane isgreat enough so that any light in the beam reflected by thepolarizer/analyzer back to the spatial light modulator gets reflected bythe imaging spatial light modulator reflection plane.
 8. The apparatusof claim 7, wherein the spatial filter comprises a filtering spatiallight modulator comprising a filter plane that is oriented opticallyparallel to the imaging spatial light modulator where a Fouriertransform of the image occurs.
 9. The apparatus of claim 8, wherein thedetector has a detection plane that is optically parallel to the imagingplane.
 10. The apparatus of claim 8, wherein the spatial filter isconfigured to spatially select light in radially extending sectors wherethe Fourier transform of the image occurs for projection onto thedetector.
 11. The apparatus of claim 10, wherein the detector comprisesa matrix of sensors and the projection lens is shaped and positioned ata location between the filtering spatial light modulator and thedetector where the image filtered by the filtering spatial lightmodulator is scaled to match sizes of sensors and/or groups of sensorsof the detector.
 12. The apparatus of claim 10, wherein: spatiallyfiltering spatial light modulator spatially filters the Fouriertransform of the image by activating liquid crystal material in selectedportions of the filtering plane to rotate plane of polarization of lightin selected portions of the beam; and a polarizer/analyzer is positionedin the beam between the spatially filtering spatial light modulator andthe detector to block portions of the light beam which are not selectedfrom reaching the detector.
 13. The apparatus of claim 2, wherein thebeam is flared before the focusing lens to illuminate the full image.14. A method of processing an optical image for isolating shape contentand characterization of the optical image, comprising: propagating abeam of coherent, monochromatic light along a beam path through afocusing lens positioned in the beam path to focus the beam to a focalpoint at a focal plane; illuminating an object image in the beam betweenthe focusing lens and the focal point in a manner that spatiallymodulates the beam of light by imposing spatially dispersed phasechanges which result in diffracted light of the object image in the beamso that a Fourier transform of the object image occurs at the focalplane of the focusing lens; spatially filtering the beam where a Fouriertransform pattern of the object image is presented; and projecting theobject image in the spatially filtered beam onto a detector with aprojection lens that is positioned with its focal points between theobject image and a detector.
 15. The method of claim 14, includingwriting the object image into the beam at an imaging plane with apixilated spatial light modulator that modulates phase of light in thebeam on a pixel-by-pixel basis to rotate plane of polarization anddiffract the light as desired for the object image.
 16. The method ofclaim 15, including passing the beam comprising the object image througha polarizer/analyzer to separate pixels of light polarized in differentplanes in order to block unwanted light and pass light comprising theobject image.
 17. The method of claim 16, including positioning a planarreflective surface at or adjacent the imaging plane and orienting theimaging plane and planar reflective surface so that the angle ofincidence of the beam on the imaging plane and planar reflective surfaceis enough to reflect any feedback light reflected from thepolarizer/analyzer to the imaging plane away from the detector.
 18. Themethod of claim 17, including spatially filtering the beam where theFourier transform of the object image occurs with a spatial lightmodulator that has a filtering plane positioned in the beam opticallyparallel to the imaging plane and that rotates plane of polarization ofthe light in selected portions of the Fourier transform plane asselected for separation from the rest of the light in the beam.
 19. Themethod of claim 18, including blocking light that is not selected toreach the detector with a polarizer/analyzer so that only selectedportions of the light reaches the detector to form a filtered image atthe detector.
 20. The method of claim 19, including detecting the objectimage as filtered by the filtering spatial light modulator on a detectorplane of the detector that is oriented optically parallel to the imagingplane, which can be physically parallel, or, if the beam is folded witha spectral mirror, can be perpendicular to the imaging plane.
 21. Themethod of claim 15, including positioning the image plane anywherebetween the focusing lens and its focal point that the beam illuminatesall of the pixels of the object image.
 22. The method of claim 21,including flaring the beam in before it reaches the focusing lens tofully illuminate all of the pixels of the object image.